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Minimal is a word that I like when it comes to electrics. I saw no reason for keeping the charging circuit and decided on a total loss system fed by a sealed 12 volt battery. Experience told me that using standard motorcycle batteries in such a system can be problematical. The batteries do not react well to repeated charging and discharging, and consequently become sulphated, and consequently useless, after a short time. Be assured, that a failed battery has lost many a race over the years! Battery For the heart of my system I used a Yuesa 12 volt standby battery of the type found in burglar alarms. These give 13+ volts consistently, and are better suited to the type of treatment meted out by a total loss system. They are also very robust and more likely to survive the vibrations of classic racing bikes. The battery was installed in a custom made holder fabricated to serve a dual purpose as a battery holder and rear wheel spray guard. I will post details and dimensions of this on the 'Plastics' page. Ignition The original contact breakers, coils and condensers are perfectly adequate for the purpose so were retained after careful refurbishment. The generator stator was removed and a thin gauge aluminium plate made up to fit in its place. The stator bears the timing marks for the ignition, hence the aluminium plate needs to be scored with a timing mark corresponding to that on the redundant stator. The rotor was retained as it required for ignition setting and performs a function within the electric start system which could not be easily replicated. (Yes, electric start.... read about it later.) A crankshaft mounted charging device such as the one on these Honda's is a major thief of power, costing as much as 5% of the bhp available. By removing the stator, I calculated a net increase of about 2 bhp at the wheel. Timing was set standard as a starting point and was fine tuned using a strobe once the engine was running. Spark plugs are standard NGK. The wiring harness was not re-used as all that is required is a simple on/off switch (two actually, see later). Switchgear A pair of linked switches were used to control feed to the coils. My sidecar racing experiences have taught me two important things. Firstly, that a race engine SHOULD be able to tick over at a modest rate with the throttle closed. It makes life so much more relaxed than having to constantly blip the throttle when at a standstill. That clearly presents an issue in the event of a rider falling, although strangely, there is no rule that says engines must cut out in such an event (except sidecars, read on). Marshals are well versed in the procedure for dealing with a running engine after a fall, they simply hit the cut out button. Secondly, I wanted a lanyard cut-out as fitted to sidecar outfits (and outboard engines) so installed one of these to work alongside the cut out button. These have to be wired a specific way and both switches must be 'Push to Make' AKA 'Normally OPEN', as opposed to 'Push to Break'- 'Normally CLOSED' as is found on more modern CDI systems. These latter systems cut the ignition by grounding the coil, an action which is inappropriate with the older system I used. A circuit diagram shows just how simple this is to arrange. Proprietary switches are available from 'Bike- It' accessory dealers or breakers.
The Push to Make Switch is the proprietary lanyard switch which disengages if the rider leaves the machine.
The Toggle Switch is the handlebar switch for use by marshalls to to cut the engine if neccessary.
It can be seen from the diagram that operating either of these will immediately cut the supply to the coils and therefore kill the motor. Starting System The starting system consists of the original solenoid located inside the ignition battery box connected to the handlebar starting switch and one half of an Anderson connector mounted on the underneath of the box. The other half of the Anderson connector is wired via starter cable to a heavy duty starting battery mounted in a box on wheels. This effectively divorces the ignition system from the starting system and leaves the ignition battery to do its job without risk of discharge from starting the engine. This type of system is common practice in motorsport and has stood the test of time. This is the Anderson connector which comes as a pair of interlocking connectors.
To start the engine, it is neccessary only to join up the two halves of the Anderson connector, press the start button and once the engine starts, break the connection. |
