This machine has been developed through years of racing, the design and materials have thus been perfected. We therefore offer the suggestions and information given below. We may at once say that the speeds attained in record breaking were not obtained without a lot of careful preparation by the riders concerned, but there is nothing to prevent anyone with one of these machines doing the same if he has the ability.
Amongst the most important things to settle is the fuel to be used. Our standard fuels are Discol R.D.1., next Discol P.M.S.2, then Petrol aviation grade mixed with 50% of goodquality Benzol. For each of these different compressions are required. Should the Discol be unobtainable some alcohol fuel may be used. It is, therefore best to use the highest compression we can supply. There are different grades of alcohol so no definite particulars call be given, but a small amount of Benzol mixed with alcohol gives good results. It is, therefore, best to start off with a high compression and experiment with various mixtures until good results are obtained. It is then possible to obtain fuel at a reasonable cost.
It is of course necessary to reset the carburetter for different fuels. For settings see Pages11 and 13.
The next point closely connected with the carburetter is the Plugs to be used. These require careful selection. Plugs are graded according to their heat resisting qualities at one end of the scale and their oil resisting qualities at the other. For starting up, a plug with the best non-oiling characteristics is best, but unfortunately, it soon gets hot,causing preignition,which soon burns up the Piston and Exhaust Valve. It is, therefore,necessary to be very careful. Plugs which stand a lot of heat are generally very expensive and being non-detachable are not easily cleaned. Therefore it is best to experiment with a plug of the detachable type, such as KLG.396, which is the best of the detachable type in heat resistance.
When running the engine it is always advisable to investigate the cause of any slowing up. The Plug is often the cause, and if it is allowed to run on these conditions, it will damage the engine, whereas, if investigation is made, the cause can be ascertained by theappearance of the Plug. Should the Plug look dry and greyish it is a sure sign that it has been too hot. If the electrodes show signs of heat. it is more than likely to be the cause.The Plug should then be changed for one that will stand more heat.
The next point is to test the tappet clearance. The exhaust tappet should have .018 to .020 and the Inlet Valve .010 to .012 respectively. Tappet clearance should be set with a cold engine.
For racing we recommend that the two Rocker pins be wired to obviate the risk of them slacking back. It is necessary to drill a hole of about 3/64" through the hexagon heads of the pins and pass a piece of wire of about 1/16" through two heads. A piece of cycle spoke is very suitable for this purpose. In the event of the piston being removed for any purpose, always replace it the same way that it was removed. The recess in Discol Pistons is to provide clearance for the exhaust valve and must always be to the front.
The Magneto timing should be checked very closely and is somewhat dependent on the compression and fuel, and to some extent the tune of the engine. Too much advance must be avoided, it will quickly overheat the engine and shows signs when riding similar to an unsuitable Plug. We recommend points just breaking with Magneto fully advanced 38 degrees before top centre for petrol benzol and 42 degrees for alcohol fuels.For Valve Timing Instructions see pages 12 and 13.
For track riding it is always best to arrange the riding position so that the smallest area possible is presented to the wind. This is most important. Even loose clothing is capable of knocking off a mile or two an hour. In order to get this position the saddle and footrests are usually placed near to the centre of the back wheel, and the handlebars arranged so that the body lies along the tank. The handlebars should not be too wide as this also offers considerable resistance.
For sprints the weight, etc. should be reduced as far as possible. If the machine is required chiefly for such events, it should be ordered with a suitable tank. For track work we find that dispensing with the weight of the front brake makes the machine easier to hold when speeds in the neighbourhood of 100 m.p.h. are reached. It is also better for sprints since weight hinders acceleration.
Apart from attention to all other parts of the machine such as chains, wheel bearings,clutch, etc., there is only the question of gear ratios to be settled. This is always best settled by trial and error. Calculations based on engine revs are only approximate. Often miles per hour are gained by careful selection. Note should be made of the wind—a following wind though only slight will enable a higher gear to be used. The same applies to a slight gradient. The condition of the surface makes some difference to the best ratio.In short races from a standing start it is generally best to gear slightly on the low side.This also applies to road racing where acceleration counts for a lot.
Before any event always run the machine gently for some time in order to get the engine, also the oil in the tank, thoroughly warmed up. For sprint events fill the oil tank only just over the line on the tank.
Timing Instructions, Pages 12 and 13
Gear Ratios, Page 13.
Carburetter Settings, Pages 11 and 13.
Lubrication, Page 12.
Racing Plugs, Page 12.