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Aluminium welding and repair

Thursday, March 18th, 2010
Damaged 1903 Renault crankcases in for repair

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.

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

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

 

1903 Renault fully restored engine mounting lug

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.

Safety Note: You should always where a mask when doing this, as aluminium dust is very bad for your body. Colin here at the workshop uses an army resparator which provides protection for the lungs, face and eyes.
 
HOW WE DO IT IN PRACTICAL TERMS; Once we have received your damaged crankcases, for welding at our workshop, the first thing is to assess what needs cutting out and what needs filling with plate or solid welding rod. Any filler plates are made at this stage to fill larger holes or voids. The crankcase or part is then heated in an oven before employing the TIG welding process. Even bearing surfaces can be made up with rod.
After welding and filling holes, the crankcase or parts is fettled to create a smooth invisible finish. Any bearing housings are machined to their original sizes. The parts are then aqua-blasted if required.
 
WHAT ARE THE EFFECTS OF WELDING ALUMINIUM?; As long as the aluminium has been prepared correctly, pre-heated, and the correct rod has been selected for the grade of aluminium, there should be no adverse affects.
 
WHAT ARE THE COMMON FAULTS IN ALUMINIUM WELDING?; Aluminium is fairly easy to weld provided the preheating and preparation process is followed. If you do try to weld a casting that has not been cut back to clean metal you will find the surrounding material next to the weld is peppered with small holes and the weld will be brittle at the join with the original material. The key to strength lies in penetration of the material, particularly on things like engine mounting bosses. If there is shallow penetration the part that has been welded will break of at the edge of the weld.  
By Terry Ives

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MOTORCYCLE RESTORATION – some advice on the so called experts & professionals

Thursday, March 11th, 2010
Terry Ives restored Ariel Red Hunter 1958

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

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!!!

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.

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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

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FOUR STROKE ENGINE LUBRICATION

Thursday, January 28th, 2010

What types of four stroke lubrication systems are there?

 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 oil pumps operate by circulating oil through a set of gears, with the gears being closely meshed within a housing of bronze or aluminium.
1. Gear Pump components

1. Gear Pump components

 
2. Piston oil pumps work of an eccentric drive pin or shaft. The pin can be commonly found on the end of the camshaft nut. This in turn drives two pistons, set within a bronze or aluminium body. The body employs spring loaded balls that sit on accurately formed seats. The balls operate in such a way as to create non- return valves through suction and pressure.
2. Piston pump fitted to a Triumph Tiger 100.

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

 

2a. Exploded view of a piston pump.

2a. Exploded view of a piston pump.

 
3. Centrifugal oil pumps operate in such a way that they need a round shaft or quill that rotates within a body made of bronze or aluminium. The shaft or quill has a spiral groove cut into its diameter. When it turns it therefore pulls oil along its length, like an Archimedes’ Screw.

 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.

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.

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.

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

 

 

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HONDA CB750 FOUR PART 7 – construction continues with the first part of the wiring.

Monday, January 25th, 2010
1. Work on the Honda CB750 cafe racer project continues

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.

Front exit for the wiring loom near the ignition box.

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

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. )

The alternator wires are run in a length of braided hose

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.

Rear Brembo master cylinder

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

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HYDRAULIC BRAKES – problems and solutions to common faults

Tuesday, January 19th, 2010
120_2099

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.

 

Pretech six pot caliper mounted on a Honda CB750 four.

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.

Rear brake stipped and cleaned for re-assembley

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.

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

 BLEEDING THE BRAKES: The main  problem people often encounter is that they struggle to bleed the brakes. They assemble the brake back on the bike and try to bleed it with no success. Sometimes this works and the brakes are fine. However you should look at the position of the bleed nipple. Air is often trapped in the calipers nooks and crannies and no matter how much bleeding you do it will not come out. Simply take the caliper off and bleed with the nipple at the highest point. Rotate the caliper if necessary until air bubbles pop out of the bleed tube. Remember to place a tyre lever or some other flat piece of metal between the pads to stop piston coming out.

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.

Brake fittings

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

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HONDA CB750 FOUR PART 6 – the start of the final build

Monday, January 11th, 2010
Things starting to come together. Engine in, front end on, oil tank in, battery in, shocks mounted, and swinging arm in.

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.

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

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AQUA-BLASTING – information & guide to this type of suface cleaning

Sunday, January 10th, 2010
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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

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.

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

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SAILING GOOSENECK – design assembly improvement

Sunday, December 27th, 2009
Standard gooseneck assembly on a 'Vortex Lazer Asymetric' racing dinghy damaged because of insubstanial mounting on the mast.

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.

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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 assembley fitted to the main mast.

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. Votex Lazer asymetric racing dingy fitted with improved gooseneck

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

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by Terry Ives

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HONDA CB750 FOUR PART 5 – the engine

Thursday, November 26th, 2009
836cc engine ready for installation

836cc engine ready for installation

The engine I have now completed and ready for installation. The crank cases were firstly striped of components and modified. The starter motor was not going to be needed so I ground most of the housing for it away. This also meant I had to tidy the generator cover and gear selector cover. The single phase alternator kit from ‘Cycle Exchange’ in the USA is much lighter than the standard item and I decided it would be left partly exposed. Have a look at the ‘Cycle Exchange’ web site, which is excellent. I have ordered parts from them and they always been very helpful. As that end of the crankshaft is in oil, the bottom case had to be welded up. A retainer for a seal was made to use the same seal as right hand seal.  In the clean up process I had the move the engine number which is mounted normally on a small raised area of the case, just behind the starter motor housing. This was all removed and I remarked the casing.

Top crank case modified to remove starter motor

Top crank case modified to remove starter motor

Single phase alternator is left exposed

Single phase alternator is left exposed

 

After a few days of grinding every casting mark and seem off the cases I aqua blasted the two halves. The cases were then painted with PJ1 silver engine enamel. This paint I think is no longer available, but Simoniz do one which is also very good. I used two tins of different silver PJ1 (0ne was plain silver, the other Yamaha silver engine paint). The barrels and head are a slightly different silver to the crank cases which makes a subtle contrast. 

The engine barrels were re-bored here by Terry and a ‘Wiseco’ 836cc piston kit was fitted. The rods were changed for ‘super rods’  from ‘Cycle Exchange’. New primary chains were fitted from ‘David Silver’ spares (probably the best source of standard parts for old Honda’s). A racing ‘Tsubaki’ cam chain with a ‘KA performance’ tensioner were also fitted. The cylinder head was fitted with ‘Kimblewhite’ 5mm stem valves and guides by Terry. These are a racing valves that  are lighter and designed to give more flow through the head. You can see a picture of the head on our gallery page. The cam shaft I choose is a road racing cam from ‘Web Cam’. An adjustable cam sprocket was used the dial in the cam to the desired overlap.

Ready for the barrels - heavy duty 'Ape' studs fitted

Ready for the barrels - heavy duty 'Ape' studs fitted

Various other performance modifications can be done, like lightening the rocker arms, under cutting the gearbox and re-inforcing the rocker box, but as this is going to be a cafe racer and not a full race bike I have decided to stay with a milder state of tune.

Most of the suppliers I have listed here are in the USA. Unfortunately it is quite hard to obtain performance parts in this country. All the dealings I had with ordering parts from the US have been pretty good, however if you do order stuff remember the import duty, the Taxman will want his cut. If you do want something that you think no one makes please ask us as about it, we can point you in the right direction or we can make most things if you can’t find what you are looking for.

by Colin Jones

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CARBURETTOR RESTORATION – the not so black art

Monday, November 2nd, 2009
Carburettors - not that scary, just time and patience

Carburettors - not that scary, just time and patience

With any carburettor restoration the first thing to do is assess the carburettor and see if it is actually worth restoring. The cost of restoration could be more than buying a new one. However if it is a hard to find one or expensive to replace then its generally worth restoring. Lots of the carburettors I have restored fall into these categories and are usually very rare or very old, therefore worth restoration.

The first step in restoration is to dismantle it. Take detailed notes on the position of all the parts and note the settings, whether they are right or wrong. A digital camera can be used to help make these easier, as a picture can tell a thousand words. The settings you get the carburettor in may not necessarily be right, but they will be a starting point. Lay all the parts out in some order that will recognise or do a sketch with arrows pointing to where parts go. Bare in mind that on old carburettors that common thread sizes were used for many jets in one single carb, so it can be easy to get them fitted in the wrong holes when putting it back together.

The next thing to do is systematically clean all the parts. I always start with the major parts, the float chamber and top half. The kindest way of cleaning and getting a great natural lustre is aqua blasting, whatever the carb is made of, brass on early machines or monkey metal on the later types. Aqua blasting is a non abrasive cleaning system that won’t remove any metal, but restores the metal giving it a durable surface that is very resistant to oxidization. Aqua blasting can be used to clean jets, needles, float valves and pins without destroying surfaces or intial sizes.

When all parts are cleaned, inspection can take place for any wear or manual damage that may have been caused by tinkering. Ignitions are often blamed for poor running, but a spark can be seen or felt. An amount of fuel passing through a carburettor is a little harder to govern.

There are some points to take into consideration regarding weld repairs to carbs if the main body leaks. Early brass carburettors are easy to weld and repair as they are generally made of quite high purity metals. Soft solder or silver is best for these. Some of the later carbs were made from zinc aluminium casting, mazak, or pot metal ( the material they used to make cap guns from). Great care must be exercised when repairing these. If it is an early mazak carb it has probably had a lot of fuel ingress in the metal. You may find that if you try and repair these with aluminium welding, TIG or gas, lumps may explode from them. A good indication of fuel ingress is on gasket faces. If under inspection you find cracks or de-lamination evident, then under no circumstances should it be welded.

Lumiweld is a low melting point alloy and the manufacturers says it can weld anything alloy. This is however not true on old mazak carbs, but is successful on later types of carb that use a little less zinc to aluminium ratio. If it cannot be welded there are some good metal adhesives on the market. I have tried most, but for carbs of the mazak or monkey metal variety I use a dental resin that works admirably well. Even stripped thread can be repaired with it.

Thankfully a lot of the inner workings are of brass. Jets are fixed objects, just controlling petrol flow, and the other bits tend not to wear to much, just needing a re-seating with a fine grinding compound, with a good clean afterwards of course. Remember that cleanliness is paramount in the fuel system governor. Sometimes, not usually, the butterfly valve shafts are worn and let the air ingress messing up the air fuel mixture. These can be remedied using bushes of any resilient material, brass or plastic, but it is very difficult to get things perfectly in line to give a smooth operation.

When all parts are clean and inspected you can start on the reassembly. This is quite simple as long as you have kept your notes, sketches or photos. New seals and gaskets should be considered when reconstructing the carburettor. I always tend to fit thin gaskets, but if thick gaskets are fitted then I would consider they are to take up deficiencies in badly mating surfaces, like trying to stop leaks on the join between the float bowl and carb top. These two surfaces should be perfectly flat. I usually file and then finish the faces on a dead flat surface plate using fine grinding compound to take off the absolute minium material. On old mazak carbs this is OK to do at the machined faces of the float bowl and carb body are usually swollen with petrol ingress. Its best to grind of the two surfaces leaving a slight witness of the old surfaces, thus ensuring you have taken of the minium material. A thin gasket with a little petrol resistant sealant on both surface can now be fitted. When bolts are tightened using thick gaskets it is worth remembering that the bolt head size dictates where the gasket is being compressed. If you had two bolts 1″ apart and you tightened them to a couple of pounds, the intermediate gasket space in between the bolts would seal. If you now applied more poundage on the bolts the more distorted the gasket would become and therefore the less sealing capacity you would have between the bolts. This is why I advocate thin gaskets on carburettors.

by Terry Ives

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