1. My Commando as it looked following its return from a 1500 mile trip to Scotland in 2008

In this blog I just wanted to tell some of you about my Commando as I ‘ve been asked about the bike by a few people. People always say “that’s a nice bike, it must have cost you fortune”. I tell them it didn’t happen overnight. I’ve been working on bits of it over the past ten years, so most of the expense is not in one hit, plus not all the parts are that expensive.

When I first saw the Commando back in the seventies I wanted one and then ten years ago I finally bought one. It was my first British bike and I was a little apprehensive about it, as I had only owned Japanese bikes from when I first rode a bike at 18. It was a learning curve and the bike I had bought was a black 850 MkIII interstate from 1977, just like the one I had seen all those years ago. Then I rode the bike  and knew it would need some of the inadequacies ironing out, so I resolved to fix the following.

The front brake

The first thing I noticed was how bad the brakes were. The standard brakes are appallingly wooden and have the stopping distance of a oil tanker. Mine had come with the Norvil 12″ disc and Locheed caliper conversion as well. After a year of riding with this set up I decided I has to improve the situation, so I could really enjoy riding the bike without having to think if I have allowed the 300 foot gap every time I braked. I decided to throw some cash at it and bought a double disc hub and 12″ floating discs from RGM in Cumbria. Front and rear wheels were rebuilt at Hagon’s and I dropped the rear one down to an 18″ wheel. The silders I got from Norvil. I didn’t buy their brake kit as I thought it looked to modern and out of keeping with the bike. I initially fitted the standard Locheed calipers, but these require the brake pads to be modified, because they hit the floating disc pins. Later I purchased the smaller racing Locheed calipers which fitted perfectly. The master cylinder, which is a lot of the problem with the standard bike was replaced with the racing Locheed master cylinder. Because the brakes were so much better I also upgraded the internals of the forks with progressive fork springs and improved dampers. I could now ride the bike with the confidence of knowing I’d stop.

2. Does it stop? - Oh yeah!!

The riding position

The other thing I found annoying with the Commando was the seat and riding position. The wind blast would want to push you down the seat and it felt like your feet needed to be 6″ further back. I did look at rear-sets, but these all seemed a bit Heath Robinson. I decided to change the bars initially to lower ones which seemed to help. When I purchased the bike I was given a King seat with it and I decided to give this a try and it was very good over long  journeys, but not the most pleasing in the eye. I would solve the riding position later in 2007 with the purchase of a Corbin saddle and flatter bars. I will talk about the 2007 rebuild later.

3. As my Commado looked in 2005. At this stage it was in Interstate trim and had twin discs with standard Locheed calipers.

The clutch set-up

After a while of ownership I found the clutch to quite heavy. I decided to try a belt driveset-up, as people told me it was kinder to the gearbox and the clutch would run dry. I purchased a belt drive kit for the MkIII from RGM. I installed it, but it soon became apparent it did not work. The problem is that the MkIII has a fixed gearbox, so the belt was almost impossible to tension correctly, even with the modified RGM gearbox bolt. The starter sprag clutch also ran very close to the belt. In the end the belt chewed itself up on the sprag, the metal wire coming out of the belt and damaging the stator. I went back to the original primary design. The left hand gearchange crossover shaft also adds to the problem and if you are thinking about a belt primary for a MkIII my suggestion is you loose the starter motor and buy an earlier gearbox cradle which is adjustable, in fact just leave the primary standard or get a MkIIa.

The diaphragm clutch also can be tricky. I have lost count of how many times I have had the clutch apart. I have had it slipping and dragging. I have tried metal plates, surflex fibre plates and bronze plates, having problems with them all. I now use modified surflex plates. Oil is also critical here I’ve found. I use Castrol automatic transmission fluid. The problem I was getting was that the plates were hydraullically locking together. I would be sitting at the lights and suddenly the bike would be moving forward, until I pumped the clutch lever a few times to free the clutch. I solved this by cutting grooves in the surface of the surflex fibre plates and using metal plates with holes in them. The oil was then able to freely flow off the surface of the plates. The keeper plate I changed for a thicker light alloy one, which I got for the failed belt drive kit, and it seems to now be working perfectly. I am now happy with my clutch, but having talked to other owners I think each clutch is a very individual affair.

The 2007 rebuild

In 2006 I decided it was time the bike was re-modelled and refurbished. I wanted it to be ready for the NOC Isle of Man International Rally in July of 2007, so I began the refit. I had been looking at a website called Norton Colorado and was very impressed by the styling and want to model my bike in that style. I was going to cost a lot of money, so I sold my sports bike to fund the build. There was not going to be enough time to build the engine and gearbox myself so I gave it to Mick Hemmings to do. I had him put the 5 speed gearbox shaft in as well. While he did that I concentrated on the rest, which would still be a lot of work.

The brakes;The wheels had already been done previously at Hagon’s and the front brakes were just requiring the new race calipers. For the rear brake I obtained a RGM rear brake mount in alloy, however because I had also decided to run Hagon ‘Nitro’ shocks it needed to be modified to fit. Once this was done I then fitted a matching 12″ floating disc with Locheed racing caliper, so both front and rear brakes matched. 

5. Wiring runs up the main frame tube

The chassis;I decided to modify the frame by running the wiring in the main tube (see photo 5.).  The spine of the frame was opened at the back end near the rear mudguard, so you could see right up the frame tube. A hole at the top was made so that the wiring could come out. Holes were also made at the rear for the tail light wiring, and brake light. The tops of the shock absorber mounts were cleaned and tidied as there was not going to be a hindged seat anymore. The ‘Corbin’ saddle mounting bar was fitted. As this was going to be a roadster now the tank and seat were fitted to ensure everything had clearance. At this stage all the frame repairs were done, to the side stand mount and the side stand spring mount. I decided to despense with the main stand. The tail light was replaced with the earlier unit with the reflectors on the sides as I thought this was a lot more shapely than the later square one. I made two holes in the rear loop to hide the wiring for the rear light, I certainly didn’t want cable ties on it. The front mudguard was changed to a cleaner steel one, which would be chromed later.

Getting it right; As I’ve said in previous articles it is important at this stage not to rush it. You need to think about where the wiring will run and how it will look. Dry build the whole thing before you paint and polish, so you know everything fits and works. Obviously it is not necessary to wire the bike, but ensure there is enough room for the wires and they will not snag or be crushed on things. Also remember the rule: MAKE THE COMPONENT FIT THE BIKE NOT THE BIKE FIT THE COMPONENT. Something make look cool and trick but if it doesn’t look right don’t use it. How often have you seen a bike beautifully built and spoiled by a ridiculous tail piece sticking up in the air at the wrong angle to the rest of the bike. I myself have bought items which I thought were great and really wanted to see them fitted to a bike, only to look at afterwards and think, why did I put that on. Most generic aftermarket or custom components  will require some modifications to fit and after you have fitted it stand back and ask yourself “does it look like the factory built it like that”. If the answer is yes then you probably cracked it, but just to be sure get a mate to give you an honest answer. Sometime you spend so long on a bike you loose the plot. I find putting a cover on it every so often and have a rest from the build helps a lot.

6. Recontruction continues - stainless battery box and 14amp sealed Varta battery are installed.

The electrical components;Getting back to the build, the battery tray had been modified previously when I first rewired the bike to negative earth and gave it a 3 phase generator. Terry here at the workshop had made a replica tray in stainless steel, but modified to mount the Boyer power box and a larger 14amp Varta sealed battery (see photo 6.). I upgraded the ignition to the Boyer Branson Micro digital ignition system form the standard boyer, mainly because I had heard about its smoothness on the Triumph T140 and the fact it replaced the Lucas coils with a smaller one coil unit. It seems to function really well and not had any problems with it. Even though the starter motor I had was a 4 brush converted one, with the 3 phase and 14amp battery it still did not work properly, so I lashed out and got a new modern starter motor from Norvil, its perfect now. The headlight I got from ‘M & P’ for £35 complete with bulb. Its an absolute bargin and is a modern flat one which gives you so much more light. The indicators were £9.99 a pair and come two different lenghts. You don’t have to pay a lot of money to look good. The ignition barrel is from a  Honda 750 four; you can get these new and they are simpler and more realiable than Lucas. The switch gear I liked when I first put them on, but it is now on my list of things to replace; they work but it looks cheap and plastic.

7. Re-enforced RGM head steady

Other bits & peices;The head steady was replaced by a RGM special. The main problem I found with this is the tube clamp is insufficient and having spoke to other owners they too have had problems with it moving on the frame tube where its mounted. Terry machined  a bigger clamp for me to keep it in place, problem solved. The iso-elastics were all replaced with stainless items and new rubbers. The ‘Z’ plates were machined out at the bottom section and a bracket for the roadster side panels was made for an old rickman fairing mount I had knocking around. A stud was welded on the lefthand side panel so that the panel is bolted on.

In conclusion I write at considerable length on my bike because of all the changes and modifications I’ve made over the years. I still have a few things to change, which I’m not happy with and it probably will never be finished. After the Isle of Man trip in 2007 I removed the idiot lights, the mega exhausts, changed the carborettor and improved the head steady. After doing 1500 miles to Scotland I changed the carborettor again. Having just come back from Spain, doing 2500 miles I’ve now have a few other changes I would like to make. It goes on!

By Colin Jones

The finished Kawasaki Z650

Here at Stotfold Engineering we don’t just work on pristine bikes. We work on many bikes that have had a hard life and are in need of bringing back to a good working standard. This one of our customers bikes. He had bought it after it had been off the road for a number of years. He required it to be roadworthy again and pass an MOT. My first assessment established the head-races were notchy and tyres needed replacing.

Once at the workshop I was having trouble getting it on the main-stand, so I got the bike on the bench and had a look. The main-stand pivot bolt was badly worn and main-stand itself needed welding. The main drive chain was examined and found to have a worn small sprocket, essentially developing a hooked shape. Further examination found the retaining nut was loose and after removing the rear sprocket it was found the cush drive rubbers were completely shot. In fact they were home made rubbers and not made of the correct grade of rubber. The nearly inch of play on the cush drive and the loose sprocket did not do the chain any favours. The aftermarket rear ‘Brembo’ brake was removed and stripped as it was seized solid. The rear light and indicators also need fixing. That was basically it for the back end or so I thought. I decided to fix the rear end first before doing the front.

1. Kawasaki Z650 rear end stripped for inspection. Not a pretty sight, but it all structurally good.

2. Rusty swinging arm, torc arm and a lot of crud

First things first. Clean the crap off ; years of chain lube mixed with road dirt. I did this with a paint brush an paraffin. Simply place a tray underneath and keep sploshing the paraffin on. I don’t bother with any of the fancy degreasers as paraffin is cheap and doesn’t harm the components. A few hours later and it was looking pretty clean. I decided the swinging arm, torc arm and main stand were  just too rusty, so once  Terry had welded some more meat on the main stand I took them to ‘Full Range Finishes’ to have them painted.

Because the main stand was to hard to use , the side stand had taken a beating. The main mount on the side stand was splayed out. I compressed it back into its proper shape and fitted a new stronger spring. The cush drive rubbers, that were home made things, were replaced with ones I fabricated from the correct grade of rubber. I then fitted a new tyre to the back-wheel and a new chain & sprockets was also fitted. Some investigation of the tail light wiring found it to be in a poor state, so whilst fitting the rear indicators I replaced the wiring and connectors.

The rear brake was proving very difficult to bleed. The Brembo master cylinder was the problem. It was full of crap and I decided not to waste time by stripping it and replacing seals. It was more cost effective to replace the whole cylinder with a ‘Gremica’ one. It was modified to fit behind the side panel. New linkages were made to the brake pedal. An hydraulic brake light switch was installed instead of the mechanical one. The electrics were also tidied up for a neat finish behind the side panel.

3. The new master cylinder installed tidied up electrics

4. Main stand repaired and repainted

The next stop was the front end. Once I had stripped it I discovered two additional problems that would need to be addressed. One of the forks seals had blown and the plastic front mudguard was cracked on its mountings. The plastic mudguard needed to be re-enforced as it is not as rigid as the original chrome one. If you are going to fit a plastic mudguard to your bike ensure it has a brace, as the forks will want to twist under load. You will notice that in more modern bikes a re-enforcing plate is fitted to the plastic mudguard as standard for this very reason.

5. The front end is removed for refurbishment

The forks were both stripped and cleaned. The fork oil had not been changed for a long time by the look of the oil. Both fork seals were replaced even though only one had blown. It’s not worth doing just the one whilst both forks are out. Cosmetically the forks did not look good. The factory finish on the sliders was lacquered polished alloy. Unfortunately this coating does not not last forever, and the position where forks are inevitably lead to stone chips in the lacquer. Once corrosion takes its toll on the exposed alloy the whole thing looks a mess. I decided now was the time to improve the looks. I aqua-blasted the remaining old lacquer off and cleaned the sliders thoroughly. The sliders were then painted silver and lacquered. This gives a clean hassle free finish which should last a good few years.

6. The front end is re-instated. A few jobs still to do.

The old steering head races were removed. These can be tricky to remove sometimes as it is hard to get a drift behind the bearing cups. These were no exception. In the end I had to cut the bottom bearing cup in half with the precision grinder. The new tapered bearings were installed and the yoke cleaned and refitted. When adjusting the head-races firstly pre-tighten the bearings loosely with a ‘C’ spanner and once the forks and wheel are in tighten again, so that the yokes turn easily with the weight of the wheel. Do not go mad they only have to be hand tight. Check the forks for play in the head stock;  loosen the yoke bolts and tighten a little more if needed. It is important not to over tighten the head-races as this produces a bad rolling effect in the bikes steering and very poor handling characteristics.

At this stage I decided to inspect the front brakes. The fluid was like old engine oil, so I decided the best policy was a strip down and clean. I repainted the master cylinder once reassembled. The top brake hose was slightly damaged and the lower ones were very rusty, so new hoses were fitted. That was the front end finished. The oil and filter were changed. The air filter and plugs were checked and found to be in serviceable condition.  Initially the bike would not start, so I checked for petrol and a spark. There was petrol in the bores, but the spark was weak and erratic. The condensers and points were replaced. Bingo! she runs sweet. A good polish and the bike was ready for MOT.

WHAT TO LOOK OUT FOR IF YOU ARE PLANNING TO RESTORE A BIKE TO ROADWORTHY CONDITION.

This bike had all the classic signs of a motorcycle that had been heavily used with no regular maintenance. If you are buying a bike like this bear in mind how much you will have to spend to have it roadworthy. Here are the most common wear points on a bike:

• Tyres – are they worn out or perished? In this example the latter.
• Brakes – are they seized, not working or are the pads worn out? All of these applied to this bike.
• Steering – is it notchy or knocking requiring new bearings? Notchy in our case.
• Forks – are the seals leaking and if so are the stanchions rusty? If they are rusty new seals will not do. You will have to replace the stanchions or re-chrome them. One seal had blown on our bike.
• Drive chain – check the sprockets for hooking on the teeth and does the rear wheel spin smoothly with no grinding sounds? The chain on our bike had a tight spot and the small sprocket was hooked.

Obviously all of the above parts of a motorcycle are parts which are take the heaviest wear, but take these costs into account before thinking you can get a bike on the road cheaply. It may not  be as cost effective as you think. Some of the Z650 refurbishment was done for cosmetic reasons, but it was just cost effective to have some of it done while the components were apart, like the swinging arm and fork sliders. It is also unlikely you will see all the faults at once. Often you don’t find them until you have stripped the components down, so allow yourself a little extra cost for hidden dangers. It is often the case with restorations that the cost out strips the value of the bike, but you must decide how much you want the bike, how perfect you want it and whether you want to do a complete restoration in one hit or do it over a number of years, riding the bike in between. I have done both in the past. My Honda 750 four cafe racer, shown here in the blog is being done from scratch. My Norton Commando on the other hand was done over a number of years, each year improving and restoring a different part of it. The latter has the obvious advantage of keeping the spending down, so not one big bill and being able to ride the bike. Always remember a bike is for riding and not wheeling out of the back of a van at shows.

By Colin Jones

Damaged 1903 Renault crankcases in for repair

At Stotfold Engineering we do weld aluminium on a regular basis and often have customers come in to have their crankcases repaired on their classic motorcycle or car. However not all aluminium is easily repaired. Firstly lets have a look at it in more detail.

WHAT IS ALUMINIUM?; Aluminiumis the most common of the metal elements on the  earth. It is used in almost all industries now, but its major use has been in the aircraft industry. Aluminium can be amalgamated with several other elements such as magnesium, sodium and zinc. These minerals give the aluminium a variety of different characteristics, changing the strength and corrosion resistance of pure aluminium.

WHY WOULD WE NEED TO WELD ALUMINIUM?; All metals used throughout industry have their weak points. Aluminium is no different. It cannot resist prolonged exposure to alkali’s and this causes the oxidised outer surface, which is acting as a protective layer from the elements to break down. Once the component starts to break down you have two choices; scrap or repair. In these days of recession repair is often the most cost effective course. Obviously, for example, to have a new crankcase cast and machined would be very expensive. However with the advent of modern materials and techniques you could end up with something better than the original. Straight replacement of parts with new is extensively employed in the aviation and MOD sector. In classic motorcycle and car restoration one tends to repair and restore due to maintaining the originality of as many parts as possible.

1. The finished repair on a engine mounting lug of a 1903 Renault

2. 1903 Renault fully restored engine mounting lug

HOW DO WE WELD ALUMINIUM? ;

TIG welding and gas welding are the most common types of aluminium welding in the restoration business. We use TIG welding for such things as crankcases or structural components and gas welding for body panels.  

• Gas welding uses oxygen and hydrogen mixed from two separte gas bottles feed a nozzle that mixes the two together. This produces a flame ideal for welding aluminium sheet. 
• TIG welding stands for Tungsten-arc Inert Gas. Firstly when aluminium castings are welded, like crankcases, it is important to first heat them in an oven to bring them nearer to the welding temperature. Then the TIG welding torch is applied with some aluminium filler rod to repair the damaged cases. Photos 1 & 2 show a repair to a 1903 Renault crankcase done by us. TIG welding is a mixture of electricity and gas. Electricity is passed through a tungsten tip shrouded by a ceramic tube.  An inert gas called argon is fed into the tube from a bottle. This gas acts as a flux so that the oxides produced when heating aluminium are kept to a minium, so keeping the weld clean and flowing easily.

HOW DO WE PREPARE ALUMINIUM PARTS FOR WELDING?; Preparation is critical, with the main goal being to cut out all the rotten parts. Think of the oxidisation as a metallurgical cancer that needs to be cut out, so only good clean metal is showing. Removal of the oxidised aluminium can be achieved with a grinder, file or burr, or even a drill, as long as one cuts out all the rot to shinny clean aluminium. When this is achieved we can put a piece of aluminium plate, cut to the shape of the hole that is left, or simplify fill it with aluminium filler rod.

Terry Ives restored Ariel Red Hunter 1958 built at Stotfold Engineering

When we require a classic motorcycle restoration to be undertaken by an ‘expert or professional’ motorcycle restorer we have to expect the complete job to cost more than the classic bike is worth. This is a very common occurrence. There are ways to bring the cost down and keep them under control to make the job more cost effective.

Motorcycling is a passion to many and to keep a motorcycle in working and running order it can cost, over the years, many times more than the bike is worth. A 30 year old bike may have had a couple of re-bores with new pistons to suit, new valves & guides, new bearings & bushes, brake linings, as well as all the usual stuff that wears out like tyres, chains, sprockets, brake pads and lubricants. When we add all this up a £1000 bike has had at least £2000 spent on it. We don’t seem very conscious of this expense due to it being incurred over a period of time.

Say you own a Triumph T140 Bonneville that wants restoring. The complete bike has been languishing in a leaky damp shed and covered with a tarpaulin causing it to sweat, or maybe you you have just purchased it as an easy restoration project. You take the engine out and think about giving it to a specialist Triumph restorer, but before you do this bare in mind what I am going to tell you.

The Specialist

Firstly before you hand the engine over to the mark specialist it is worth bearing in mind that all engines work basically in the same way; they have a spark generator, pistons, con-rods, crank, and  cases which sometimes have an integral gearbox. The mark specialist knows his engine building off by heart, he does not need the ‘Haynes’ manual and he will bill you for his ability in not using one. His restoration job is easy, he may have a stock of secondhand as well as new parts he has bought in for future rebuilds. All these parts are paid for through your engine rebuilds and he can put in any parts either fine used or new into your engine. Who are you to argue as he is the specialist. The ball is in his court because whatever he says about the engine he has rebuilt for you, he is right in every way, including the bill. Why do people become specialists? Well in my opinion it is the only engine they know how to build or they are catering for a captive market. If it is the only engine they know how to build then they have a very limited ability and are incapable of venturing out of their skill base. If it is for a captive market, it can only be for money.  We all have to earn money and make a profit, but think, the specialist is usually a limited supplier of new parts. He often does not produce the parts himself and will mark up parts by 100% that he has bought in.

The thoroughbred engine restorer has studied engines, how they work and if need be how to tune them to get maximum performance or to their customers specification. He can work on any engine, they are all basically the same, but if he gets stumped can always look it up in a manual, on the web or can use his skills that he has acquired through books and technical college to resolve the problem.

If one is to specialise in one particular engine he will have a very limited amount of tooling. The tooling will comprise of all the factory kit and maybe some special tools that have been made to the builders requirements. He will have a basic fly press for pressing bearings and bushes in & out of cases. He may have an oxy-acetylene torch for heating up cases and welding up broken pieces of frames. A lathe, albeit a small one, probably a bit bigger than a model makers to turn up bushes and guides. This is what is needed bey the specialist, but what happens when he needs a barrel relining to standard, re-boring and honing. Where is he going to send the crankshaft that needs about 30 tons per square inch to push the big end pin; to the crankshaft specialist. What happens when he needs a two stroke cylinder liner replacing on a high performance racer and the ports have to be replicated to the standard tuned opening times, you guessed it; the specialist in this field. All the specialist input racks up the bill to the customer.

• Case study No.1 (stories from our customers)

A customer gave a petrol tank to a classic motorcycle restorer for restoration. He sent it out to a specialist tank restorer. They did all the work of lead filling, chrome plating, painting and lining the tank. Six weeks later the tank was given back to the customer with 100% cost and VAT added. The customer was happy with the job , but ignorant of the real cost. Moral of the story is if the customer had spent a little time looking for the specialist tank restorer he would have paid alot less for the same job. Looking on the web, classic motorcycle magazines or word of mouth are starting places. Obviously asking if it was going to be done in house is also a good idea.

• Case study No.2 (stories from our customers)

A customer takes his Norton Commando to a motorcycle restorer. He tells him there is a slight misfire at high revs. Restorer say he will look into it. He returns to collect the bike and is give a bill for £427.53.  Hells bells!!! for a misfire. New parts are coils, Boyer ignition system, HT leads and plug caps. Twelve and half hours labour?

It amazing what some restorers will charge

Unfortunately not taking the hint after the first bill the customer goes back to a motorcycle restorer because it is running poorly again. He tells the restorer it does not seem to run smoothly and the electric start seems noisy. Restorer says no problem I will sort it out. He returns to collect the bike and is handed the bill for £490.48. New parts spark plugs, needle jet, main jet and sprag clutch. This time 14 hours labour! Smacks of someone just bolting new parts on until the problem goes away and how often to replace a needle jet on a Mikuni carb!

An oceanic bill? YES!!!

Finding the right people

Lets look at the engine. If you could find a workshop that does precision engineering with a mechanical background as well you would probably find they have made parts such as percision crankshaft parts and have fitted special sized plain bearings into crankcases. Basically what I’m saying is you don’t need to go to the one mark specialist. If you have a classic bike and it in need of a full restoration, do what is most cost effective; find the tank restorer, find the cylinder refurbisher, find the frame striaghtener & weld repair specialist, find the cylinder head restoration company, look on the web and search for that aluminium welder to repair your crankcases, download information on local seat restorers.

You may be lucky enough to discover a local company that will do most of these things, including wire wheel building and classic bike electrics. If you do find one you will be quids in on your restoration project, because a company that genuinely say what it can do in house is going to get enough work from your restoration project at a reasonable profit and will not be afraid to divulge what they cannot do. They may also point you in the right direction or recommend a specialist in crank grinding or local paint sprayers for example. After all classic motorcycle restorers all know each other in one way or another and know of the specialists who carry out the work that we cannot do or do not have the knowledge or specific machinery to do.

When you approach a classic cylinder head restorer you will evidently see the associated machinery to do the job. He would be pleased to show you how the machinery works and some work in progess or completed. He should be happy to do so, as you are a prospective customer and he make a living from you, so your experience will generate more work for him by you telling others how good he is. When you walk  into a motorcycle seat restorers workshop you will expect to see vinyl’s,leather cloths and industrial sewing machines throughout. But if you walk into a classic motorcycle restorers workshop I bet you will not see a chrome plating shop, a person building wire wheels and someone on a lathe making crankshaft parts. All these specialist fields are undertaken not by the classic restoration company, but by specialist is their respective fields and this will cost you as the classic bike restorer marks the stuff up as the middleman.

The restorer who says he perform complete restorations is talking a load of bull. He would be a lair as we would if we said Stotfold Engineering can cast you a new crankcase, but we know someone who can and would be happy to point you in that direction as long as you gave us the opportunity to quote on the machining of it.

As I said previously if you can find a company that can carry out most of your requirements in house you are lucky. We at Stotfold Engineering consider ourselves to be one of those restorers luckily. We sub very little out in respect of the restoration and refurbishment of classic or custom motorcycle and cars. Are costs are generally lower than the specialists. We don’t have shinny polished floors, advertising memorabilia, boxes of brand new ‘Snap On’ tools, customer coffee machine (although if you ask we might make you a cup of tea) and immaculate boiler suits, because we don’t believe in the bull**** baffles brains concept. We get on with the job as true enthusiasts. As you can see some our machinery is not what the average restorer would have.

Things to watch out for before you sign up with a classic motorcycle restorer.

1. Is the company a one man band? – One person cannot do all aspects of the work and will therefore sub work out and cost you dearly. You will pay for the specialists he knows and uses.
2. When you walk through the door are you made to feel welcome? -  Someone who immediately welcomes you and shows interest in the work you want doing wants your custom. He doesn’t keep you waiting while he’s on the phone in the office chasing up subbed out work.
3. Is the proprietor happy to show you the machinery they produces the work on? – If they use excuses like ‘that aspect is done at our other workshop’ or ‘health and safety does not allow you to enter’, beware!!
4. Are there lot of bikes on the premises under construction?- Motorcycle restoration takes a lot of time to finish a bike off and get it off the bench. If you have been getting parts of your project restored by the same restoration company keep an eye on how other customers bikes are progressing and don’t feel out of place asking about them. He may say it is for himself or a long term project. Colin, here at the workshop has a few bikes of his own he works on, as do I. However there is a company I know who has had customers bikes on the workbench for a number of years. The customer of the bike could not afford the astronomical bill and as no quotes were given for the restoration was unable to pay.
5. Is the propreiter happy to divulge specialist suppliers in his initial quote? – If they are cagey about this, then they are planning to be the middleman and this will be costly for you. Do a web search and look around for specialists. The honest company will know you may check the price with the specialist supplier and it will unlikely to rip you off. Bare in mind however that quote over the phone and without the specialist seeing them can be considerably different. You cannot quote on something you cannot see the condition of. Some suppliers will give you a very cheap quote just to get you in the door and then add addition costs to bump up the price.
6. Are they willing to give you a rough cost estimate on the refurbishment of a particular part or the re-manufacture of that part? – If you don’t get a rough quote, listen to their patter. “It won’t cost too much” or  ”it won’t take long to do” are really not much use. Ask them to give you a quote for the most it will cost.
7. Do they give the old parts back? – A good restorer will be open and honest with you. He will hand you back all the old parts he has removed to show what he has replaced and show its condition.

Full restorations are very hard to quote on. It is often the case that until a bike is completely stripped that you know the extent of the work that needs doing. A restorer will not a quote for the whole job as there are too many variables in what he cannot see. He is unlikely to quote you a huge price, which would put you off using him, but may have a flat rate for the basic engine strip and build without parts and specialist repairs, which will be extra. If you supply your bike broken down for inspection supplying notes on what you think needs repair he should be able to give you a fairly accurate quote. If he cannot quote on say a crankshaft repair then he will be subbing it out at your expense.

Another pit fall to watch out for is the restorers hourly rate. These mean nothing to the restorer as he can model his final bill to justify his rates. He says his hourly rate is £15.00 and you say that’s cheap, do the job. The only problem is he gives you the bill for £150 and says it took 10 hours to adjust the carburettor. As shown earlier in case study no.2, the so called restorers of classic motorcycles are only to willing to make up for their lack of business to rip you off. Remember it is very hard for a classic motorcycle restoration business to survive on restorations of bikes alone. There just isn’t enough work to go around, so those that do will want to make the most money from you.

I hope you find what Colin and myself have said to be use in enlightening you on the practices of classic bike restorers. Stotfold Engineering is lucky enough not to rely solely on bike restorations, even though it is our passion. Our versatility allows us to carry out a multitude of different services not only on classic motorcycles. I hope one day you will test our services and would be pleased to be put to the test on the seven points I raised earlier.

Stotfold Engineering looks forward to the comments aroused by this publication from the professional classic bike restoration faternity and prospective customer alike.

By Terry Ives with input from Colin Jones

 There are four main types that are used on four stroke motorcycle engines:

1. The  splash or spray system
2. The total loss system
3. The dry sump system
4. The wet sump system

1. The splash or spray system of lubrication: This was employed in the earliest days of engine development. The system comprised a sump or crankcase with a set amount of oil enclosed within it. As the rotating crankshaft and connecting rod dipped into the oil at the bottom of the stroke it picked up and lubricated all of the lower parts of the engine. This type of lubrication under went small design modifications. These included a rod which extended down vertically from the big end bearings, dipping into the oil in the sump and therefore picking up a little more oil. There  were several designs of these. There are also accounts of con-rod and flywheel modifications. These were done for the sole purpose of getting the oil higher up the crankcase. The inherent side effect of this system of lubrication is that the crankshaft was subjected to oil drag as it splashed through the oil in the bottom of the engine.

These early engines employed mainly white metal and plain bronze bearings with crude seals. They were slow revving, being low in performance as well as in crankshaft and gearbox speed. As engines developed, the customer and therefore the manufacturer required more speed and with this came higher revs. The stroke of the latter day engines had to be shortened to attain these revs. With the increase in revolutions came increased performance and higher piston speeds. Basically all the internal workings of the engine were subjected to higher rotating and reciprocating speeds.

Oil development and improvement had crept a long with improved engine designs. The ball type bearing had replaced many of the plain bearings and seals were becoming more effective. A more modern lubrication system was required the keep up with the performance changes.

2. The total loss system: was employed for these more advanced engines. They used a simple oil pump that was hand operated. A typical vintage motorcycle users manual of the day stated that at normal riding speeds (20mph) one pump of oil was needed for every eight to ten miles and at higher speeds (30mph) a pump was required every six miles. The oil for the pump was fed from an oil tank. Before starting one of these engines you had to give it a pump of fresh oil. This topped up the splash lubrication system in the sump, which was still being used, and took care of the bottom half of the engine. Drip feed lubricators were often used in conjunction with hand pumps and were normally set to eight drops of oil per minute.

When using just the manually operated pump, the early motorcyclists sometimes it was found that the engine would run faster if less pumps were given, but only for a short while. This was due to there being less oil drag on the piston and other moving parts. If you were lucky you could flood the engine with a couple of extra pumps to make up for the lost ones that had given you the extra performance that all the early motorcyclists craved for. Oil had to be be more accurately governed and manufacturers decided if this could be done their engines would be more reliable, therefore not leaving a bad reputation for reliability in the hands of  their customers.

3. The dry sump system: was one of the first to be mechanically governed. This system uses two pumps. One feeds oil from an oil reservoir under pressure to lubricate the engine before dropping into the sump. The second pump or scavenge pump then picks up the oil to return it to the reservoir, sometime via the transmission or other parts of the engine that require lubrication. you will find on dry sump engines the scavenge pump is double the size of the feed pump. You should be able top see the scavenge pump working by removing the oil tank filler cap and observing oil being fed back into the tank.

When dry sump engines are laid up for a while there is a tendency for them to back flow on the scavenge side (wet sumping). When you start the engine with a dry sump that has sat for a while and you cannot see any return flow coming into the tank, pour a pint of oil in and wait until you see return flow activity. Then adjust the oil level with a siphon or draining.

4. Wet sump lubrication: was the next development and removed the necessity for an oil tank. It seems to be the most popular system for Japanese motorcycle manufactures. The oil is contained in the crankcase sump, however it is separated or masked from the crankshaft, so as to prevent oil drag and any frictional losses from the oil splash. A pump oils the engines vital components and returns the oil via a filter back to the sump for recirculation.

What types of oil pump are there?

There are four types of oil pumps commonly found on motorcycles. These are:

1. Gear oil pumps
2. Piston oil pumps
3. Centrifugal pumps
4. Trochoidal pumps

1. Gear Pump components

2. Piston pump fitted to a Triumph Tiger 100 being restored here at the workshop.

 

2a. Exploded view of a piston pump.

 4. Trochoidal  pumps work with a star shaped gear attached to the end of a shaft. The gear is rotated within a metal body which has the same star shape cut into it, but bigger. The body of the pump, usually steel, also rotates within another housing, which is usually aluminium and machined into the engine cases. Oil enters the body and is pressurised in between the finely machined faces on the star and is forced around the engine via outlet ports.

4. Trochoidal pump components. This is the most common now for modern motorcycles.

 Oil pump restoration and repair

When repairing oil pumps, whether it be for cars or motorcycles, the first thing that has to be done is t o remove it from where it is fitted. The next thing to do with the pump while it is a complete unit is to look at its overall condition. Are the any knocks or dents that might have occurred while removing it. These dents may cause distortions or bad running clearances on shafts or gears within the their housings. When you look at a pump dents or knocks are not always clearly evident, as the may be black oily residue covering the pump body. These oily residues can usually be scrubbed off with petrol or paraffin. Here at Stotfold engineering we aqua-blast them clean. This helps identify any marks on the pump casings. The pump internals are washed in paraffin and blasted with high pressure air.

A gear pump stripped for restoration.

Prior to aqua-blasting the pump should be stripped down completely. Take notes on how it come to pieces and lay the parts out, so that you recognise them for reassembly. Use a digital camera if you think you will forget. Once all the parts are laid out it is time to clean and inspect them, taking note of wear and running clearances. When we rebuild pumps we always set running clearances to 0.001″. This leaves enough gap for hot oil to get between all of the running and pumping parts. It is worth taking into consideration that if any parts such as spindles or pinions are worn, they can be precision ground to just clean them up. The holes they run in can be then bored out and bushed to suit the new spindle diameter. I have not yet found a pump that could not be restored.

Fully restored oil pump completed by us.

It is now time for reassembly. Each part has been meticulously cleaned and checked. Once reassembled, with any nuts replaced or wired up if necessary, it is time to oil it and run it to see if there are any tight spots. This can be done using a drill on low speed. Then check the it operates freely using  just your hand. It should run freely. You can now reinstall the pump.

By Terry Ives

1. Work on the Honda CB750 cafe racer project continues

From day one of this cafe racer project I have always had it in my mind that all wiring should be well and truly hidden. To many really good creative bikes are made with little or no thought for the wiring. I like my wiring tidy and when ever possible hidden. When you decide to build the bike you have always wanted, or a bike you think that manufactures should have made, some elements of the build will always be compromised by budget, the shear practically of the idea or the simple fact it would take to long to make.

Too many people are fearful of wiring and hence it is usually one of those areas of a bike that gets neglected. If you are prepared to spend a little time and effort a neat and tidy custom loom can be made. The basic equipment for making your own loom is an assortment of different coloured wires, a soldering iron, solder, heat shrink, electrical tape, and a few connectors.

‘Vehicle Wiring Products’ have a good range of various electrical supplies and can be found on the web. To save money, if you can find a scrap car, you can remove its wiring harness and recycle it. Ideally new cars that have been written off, so their harnesses are quite new. This will give you a variety of colours and the harness will be longer than a bikes, so giving you plenty for adjustment. Wire where the copper core has gone black and tarnished should not be used. It will be hard to solder and will be more prone to failure.

Connectors are really not that important, as you can solder all wiring without using them. The advantage of no connections is that there are no breaks in the wire and the potential for corroding connectors is avoided. The disadvantage is that if you have to remove a part it will need to be cut off and re-soldered back on. I have built bikes in the past with no connectors and aimed to keep all wires as intact as possible. There is good sound reasoning for this. Any break or connection in a wire creates resistance and the accumulative effect of this is voltage drop. For example, if you have a poor headlight output; you change the lens, the bulb and think the application of a fully charged new battery would cure it.  You failed take into account the half a dozen old connections between the battery and the bulb. It might have been more cost effective to replace the wire between the two with new wire with less breaks.

Manufactures of motorcycles tend to have plenty of connections and redundant wires. The reason being is that they have to sell their bike in many different countries and so need to add extra or different parts to the same model of bike. If you construct your own loom you can eliminate these unnecessary wires and simplify others. The routing of the cable can be improved too as they are often placed for ease of manufacture. There is nothing worse that seeing a load of cable ties on a frame tube. It smacks of poor design and lack of thought, hence wiring should be of equal importance to that flash end can you got for your exhaust system. In the planning stage of custom bike building it is one of those thing often overlooked.

2. Front exit for the wiring loom near the ignition box.

For my bike the wiring will be as simple as possible and run where ever practical in the frame tubes. I planned the route of the wiring in advance when I was modifying the frame. The main harness will run up the main tube under the tank and exit near the ‘Boyer’ ignition box.

3. The finished wiring for the 'Boyer' and coils. Tidiness is next to Godliness

I decided not to use the con-volute tubing for the harness in the end as shown in photo 2. I heat shrank the whole lot and used the plastic braided harness cover for the length from the head stock to the headlight. One of our stainless steel clips was then used to hold the harness in position. The whole resulting wiring is neat and tidy with the minimum of connections ( photo 3. )

4. The alternator wires are run in a length of braided hose

The wiring from the alternator was a bit of a problem but was solved by the use of some braided hose to make a feature of it. A piece of aluminium tube and a stainless ‘P’ clip were used to secure the bottom of the hose covering the wires.

5. Rear Brembo master cylinder - the stop light wires run in the frame tube.

The rear brake light switch is fed by a wire running down the rear diagonal down tube and exits near the ‘Goodridge’ brake light switch. It is one of the bits of visible wiring, so I covered it with a rubber boot.

Switch gear is keep to a minimum, with the lights wired on permanently, so only a high/low beam switch is required. The other switch required is the engine cut switch and horn button. In the next part I will show you how the rear is wired, the switch gear wire is fitted and how the headlight is arranged.

By Colin Jones

1. Norton Commando double disc conversion.

 From time to time we get the same inquiries about various aspects of motorcycle building. Brakes is one of those subjects. People come into the workshop, phone or email saying ‘my brakes are spongy and how can I fix them’ or ‘my brakes work, but what can I do to improve them’.

Photos no.1 shows my Commando double disc conversion. It features twin “RGM” 12 inch discs with “AP Racing” calipers mounted on “Norvil” sliders. The master cylinder is “AP Racing”. Believe me the bike stops.

2. Pretech six pot caliper mounted on a Honda CB750 four.

Photo 2. shows my Honda CB 750 four featuring a single “Pretech” six pot slim back caliper operating off the original disc and master cylinder.

Both of the above are vast improvements on the original brakes. However some people are very reluctant to even touch the brakes as they think it will cause them to fail and crash as soon as they ride the bike. It really is not that complicated, but if you are at all unsure of you own knowledge or abilities it would be best to speak to us or bring it in for us to work on.

The most common faults which lead to poor brake performance are the following:

• Air in the system is the most common of them all. This is caused by the brake not being bled properly after a rebuild, or a loose connection on the hose lines, banjo bolt or bleed nipple  allowing air into the system.
• Sticking pistons in the brake caliper allowing the pad to constantly run on the disc, causing friction and heating the fluid. The fluid boils and generates air bubbles so leading to spongy brakes.
• Leaking fluid from the master cylinder seals or piston seals allows air into the system.
• Worn out or tired brake hose. These degrade over a period of time so leading to greater expansion of the hydraulic fluid and loss of performance.

Obviously these are the four most common problems. Physical damage, like an accident can also lead to problems or just bad positioning of a brake hose leading to it rubbing on another part of the machine.

SERVICING YOUR BRAKES: Once you have stripped your brakes, clean them thoughly and blow small oil ways through. Cleanliness is important as any dirt will cause damage to seals and reduce performance. Once reassembled with new seals, ensure firstly that all connections are tight. Use new copper washers on banjo bolts and make sure the bleed nipple is clean and not blocked with road crap. It is common for them to get blocked, especially if the caliper is mounted under the swinging arm, where it is punished by road dirt. This position on the bike will also be rough on the pistons and this is often the cause of seizure. Some bikes will have gaiters on the pistons to help protect them, but nowadays this is not often the case.

3. Rear brake stripped and cleaned for re-assembly

4. Finished rear brake assembled on the CB750 cafe racer project. Modified from an early Suzuki RGV250.

Speaking of equipment for bleeding, I have always used a length of clear plastic tube only, no non-return valve or fancy pressurised kits are really needed. Just ensure the tube is tight on the nipple head and long enough for the end to sit in the brake fluid bottle. However it is easier to bleed with two people.

The procedure: No.1 presses  the lever down. No.2 opens the nipple, allows fluid and air out, then shuts the nipple. No.1 then lets the lever out. The cycle continues until all the air is  removed and the brakes are firm. Every so often stop and just pump the lever to see how firm it is getting. Obviously the fluid is topped up as you go. A problem you may encounter is that the fluid may become air rated and fully of tiny air bubbles. In this case just leave it to settle for few hours before going again. It amazing what an overnight break can do for an air lock. Some calipers have two bleed nipples for each side of the caliper and this can be useful for easy removal of the air.

If you are still having problems getting the air out, stop a while, check the system for oil tightness, if all is OK then sometimes hanging the brake caliper with the bleed nipple at its highest point and tying the lever back under load over night can help.

5. Various brake fittings

BRAKE FITTINGS : Most people nowadays upgrade their old rubber hose with new higher strength braided hose. I use “Goodridge” build-a-line hose now as it much easlier to fit and is easily obtained off the shelve from most motorcyle shops now. You can see the new build-a-line hose on the left in photo 5. The older hose, on the right in the same photo, was harder to fit as the banjo had to be postioned exactly in the right position for it to prevent the hose being twisted when fitted. With this new hose you simply bolt your banjos in position and then screw the hose on. Motorcycle shops sell it in all the common lenghts and it comes in 25mm increments. Banjos are also sold in various angles.

By Colin Jones

Things starting to come together. Engine in, front end on, oil tank in, battery in, shocks mounted, and swinging arm in.Forward view of the construction. Wiring and exhausts are left for later.

Forward view of the construction. Wiring and exhausts are left for later.

Finally I have reached the stage of reconstruction. The frame has returned from the painters (’Full Range Finishes’ – Letchworth) and the swinging arm freshly chrome plated (’Doug Heath’ – Baldock). Firstly the frame was prepared with new head races and all the threads cleaned. The engine was placed on the bench on its side. The frame was then lifted over the engine. This is the easiest method of putting the engine in the frame without giving yourself a hernia. Items like the alternator, oil pump, clutch, oil filter and sump pan can be put on later. Anything to keep the weight down for insertion into the frame. Once in the frame, all the above parts were fitted.

I then put the front end back in complete, as I had already finished and assembled it. The oil tank was then fitted and the hoses to the engine and the oil cooler were also put into place. The modified ‘Dresda’ swinging arm was fitted with the ‘Hagon Nitro’ shocks. The custom battery box and battery were mounted. The 31mm CR special carburettors are mounted and connected to the throttle linkages. I then placed all the electrical  components into place; the micro digital box, single phase regulator and micro coils. The rear sets were then fitted to the rear frame hangers.

Next time I will talk about the wiring and some of the teething problems I have encounted. Until next time, wishing you all a happy new years motorcycling.

By Colin Jones

Stotfold Engineering's Aqua Blasting machine. 'Comet' wet blasting unit made by Abrasive Developments Limited.

NAMES: Aqua-blasting, also known as vapour blasting and wet blasting.

WHAT IS AN AQUABLASTER?: Essentially it is a machine that operates using a medium compressed air supply and a high pressure pump. The sump of the cabinet type aqua-blaster contains water and a measured amount of media. The water and the media are mixed in the sump. The high pressure pump forces the mixture through a rubber hose to the gun, which is usually manually held via  two apertures in the cabinet that have rubber gloves fitted on flanges inside. The whole cabinet is rendered waterproof through the rubber seals to the side door. The door is for loading any work or article into the cabinet. Aqua-blasting cabinets normally have a rotating table within the center of the cabinet. This is used to rotate heavy items, such as engine casings or other difficult to maneuver parts. The table is normally rotated manually by the operator.

HOW DO AQUA-BLASTERS CLEAN?: Aqua-blasters clean materials as well as surface etch. The cleaning process takes place when water and the media are passed through a nozzle at high velocity. The velocity is important and can be made manually through air intake pressure adjustments. The nozzle, which is made of tungsten, guides the water and media in a controlled stream. When this stream of water and media is directed at the surface of the item to be cleaned. The surface of the item is subjected to an erosive affect.

The point of putting parts through this erosive or scrubbing cycle using aqua-blasting is to clean them down to the original base material. For example we were given a ‘Primus’ camping stove that had heat proof paint on it. The camping stove case was made from very thin metal and would not stand up to aggressive treatment, such as shot or sand blasting. The aqua-blaster was set to just strip the paint down to the base metal. This is done by controlling the air pressure or adjusting the distance the nozzle is from the work. The paint was stripped and only the bare metal was visible. Now the bare metal had to be subjected to the erosive effect of aqua-blasting. This was procured by playing the nozzle and fourth across the item until the desired satin finish was to ones liking and all the paint and rust had been removed.

The erosive or scrubbing affect on the surface of bare metal, when you get through the layers of paint or rust, is non-aggressive, in other words it does not have an adverse effect on the surface structure of the base metal, in fact a beneficial effect. 

WHAT EFFECT DOES AQUA-BLASTING HAVE ON MATERIALS?:Take a set of crank cases for example. When they are sand-cast, they were left to weather or age before they were fitted with all internal components, as were the cast iron parts such as the cylinder liners and cylinder heads. The natural aging of these parts was crucial to let them settle down and loose all of the inbuilt stresses created through the casting process. Later modern castings are pressure fed die castings for greater mass production. These have lots of stresses in them and they retain them.

I was given a set of die cast crankcases to experiment on. Firstly I cut through the fly wheel housing with a milling cutter. I then measured the amount of distortion caused by this machining. I then took the same cases and aqua-blasted them. I then replicated the previous milling machining on the flywheel casing. The amount of distortion on the aqua-blasted case was 75% less than on the non-blasted case. This bares out the advantages of aqua-blasting. We have however had not problems with distortion on sand-cast castings, whether aqua-blasted or not.

Triumph T140 crankcases aqua-blasted

 Aqua-blasting not only cleans down to the base structure, but also normalises it. The scrubbing action of aqua-blasting on the base metal is found to have no adverse affects on material stability, whether it is in thick or thin sections.

When we propel a media alone, such as shot or sand-blasting without having water involved, the media hits the object at a force of its given velocity. When the impact of the media takes place on that object it will have an adverse or restructuring effect on the material it bears on. The application of water into the mixture gives a cushioning effect to the blasting process, allowing all impurities on the surface to be removed without damaging the structure of the material.

A Ducati Mach 1 engine being restored here at the workshop. All the main engine parts were aqua-blasted before assembly.

WHAT MEDIA PRODUCTS DOES AQUA-BLASTING USE?:Almost anything can be used in conjunction with water to produce a clean satin finish. Varying the media has only a slight affect on the final product finish. Media’s include; glass (150-200 micron), calcium carbonate, olivine, almandite, garnet, and aluminum oxide. All these produce a nice satin finish that is sought after by the classic motorcycle and car fraternity.

WHAT CAN AQUA-BLASTING CLEAN?:Aqua-blasting struggles on some paints, most of all powder coating and also some of the casing paints found on Japanese motorcycle engines. We usually use a stripper, such as ‘Nitromors’, to remove and soften the coating before finishing with aqua-blasting. Sometimes this require several re-applications to fully clean the object and it can be quite time consuming. Aqua-blasting  cleans the gummy lacquers from carborettors and most paints from steel and aluminium surfaces. Oil stains on engine cases and con-rods can also be removed.

WHAT SHOULD YOU NOT AQUA-BLAST?: There is no discernible change in diameter or bore on objects after aqua-blasting, however surfaces that require running fits and tight clearances should not be touched with any type of blasting equipment. They should be masked off with tape or covered. The following should not be aqua-blasted:

• Big end bearings : although needle roller cages can be blasted.
• Pistons : the reason being it upsets the diameter patterns of the circumferential grooves that pick up oil to lubricate the piston skirt.
• Small end gudgeon pins
• Any white metal or lead bronze materials that have a bearing surface
• Valves: unless the stems have been masked of.

WHAT ARE THE MAIN USES OF AQUA-BLASTING?: Aqua-blasting is used mainly in the restoration, renovation, and preparation of metals and some other materials. Aqua-blasting has also become favourable for graffiti removal.

At Stotfold Engineering we cater for classic and vintage motorcycle and car clubs. Work includes engine & gearbox casings, crankcases, engine covers, barrels, carburettors, frames & swinging arms and many other vehicle components. Any stripped down basic component can aqua-blasted by us. We can aqua-blast steel, brass, titanium, aluminium and cast iron. If we repair aluminium or cast iron for you we can then finish the item off with aqua-blasting to hide any signs of repair.

WHY IS AQUA-BLASTING MORE ADVANTAGEOUS THAN SHOT-BLASTING?: Firstly shot-blasting is a destructive process. It erodes metal surfaces, leaving them open to further corrosion, unless immediately painted with a phosphate type paint. Shot-blasting produces dust, heat and releases toxic bi-products into the atmosphere. It also wears out hoses and nozzles at a greater rate and so this cost has to be passed on to the customer. Because aqua-blasting uses a aqueous media it does not produce dust or heat. Heat produces rust  on bare metal surfaces. With aqua-blasting there are not toxic or chemical compounds to attack the atmosphere or earth as the bi-products are filtered out by a special water trap. Aqua-blasters run for hours on a single fill of media; grit, bead or glass etc..The aqua-blasting nozzles and hoses last thousands of hours longer than the equivalent shot-blasting fittings.

WHY IS AQUA-BLASTING MORE COST EFFECTIVE?: As previously explained there is less waste, less wear on parts and no toxic wastes. All of these factors have a positive impact on the customers costs.

HOW SHOULD THE PARTS BE CLEANED AFTER BLASTING?: It is imperative that all parts are meticulously cleaned after using any grit based cleaning. After general rinsing and washing grit can still be lodged in small orifices like carburettor jets, oil ways and any other small cavities and voids. Stotfold Engineering, after aqua-blasting, completely removes every particle of grit from parts by washing in paraffin and then ultrasonically cleaning them. Sound expensive, but you should take into account that an engine can expire very quickly from a few particles of grit. Here we also recommend that any new build engine should be started and run, on any cheap mineral oil of the correct grade, brought up to working temperature and then have the oil and filter changed. This allows the engine to be fully flushed of any possible grit contamination.

By Terry Ives

1. Damaged gooseneck assembly on a 'Vortex Laser' assymetric racing dinghy.

A customer approached us with a damaged gooseneck assembly from his ‘Vortex Laser’ assymetric racing dinghy. The damage to the fitting was caused when the boom swings over too far and attempts to pull the gooseneck from the mast. After a few of these mishaps the whole assembly gets badly distorted and the retaining mast rivets become loose, so adding to the problem.

2. Re-designed gooseneck assembly next to the old standard fitting (damaged).

 Looking at the design of the assembly it found to have a very small bearing area on the mast, so obviously this had to be increased to spread the load. The whole assembly also needed to be a lot stronger using thicker stainless steel and adding some cross members. All the customer had to supply was the old gooseneck assembly and a template of the mast section, where it was originally mounted. As you can see in picture no.2 the new assembly is a lot stronger and more substantial, giving a greater bearing area on the mast and only being marginally heavier than the standard item.

3. New assembly fitted to the main mast.

The new assembly has also been constructed with full weld runs rather than the tack welds employed on the standard item and uses 10 rivet holes on the mounting plate instead of the original 6 holes (see photo no.3).

The product was manufactured by laser cutting the profile shape and TIG welding the components together. The whole thing was then aqua blasted to give it a clean satin finish. The last two photos below show the gooseneck assembly fitted to the mast and boom ready to compete in the ‘Construction Industry Sailing Regatta’ at Rutland  Water.

4. Vortex Laser asymmetric racing dingy fitted with improved gooseneck.