Originally Posted by dpohlson
So you're saying it is possible to not only remove the starter motor, but ALSO the charging system, and the fuel pump with some mods to the tank? That's great thanks.
I will search around for the fuel tank modification you're referring too. Is it a matter of venting, or actually cutting and re-welding the shape of the tank? I'll have to pull out my tig welder, study my electric diagrams too.
There is no point in removing just the starter motor as the minor weight loss is barely offset by the problem of starting the engine by alternate means.
I race my 929 without the charging system or starter which saves almost 8kg. The 929 starter motor is only 1680gms. Removing the starter clutch, solenoid and idler saves another 700gms. The alternator rotor though is nearly 1800gm of extra weight on the crankshaft - making it almost 25% heavier.
You only need the pump because the fuel in the tank is below the height of the float valves in the carbs. If you keep your fuel above that level you don't need the pump.
If you were running without the charging system then it may be worth modifying the fuel tank so as to do away with the pump to conserve battery power.
I would suggest running without the charging system to see how long the battery lasts first as it may not be necessary to worry about the pump.
The 929 though is injected with a high-pressure pump so it really saps battery power - thirty minutes is about all the battery is good for at race pace with bump starts.
Alternatively, you could perhaps run a second battery just for the pump.
How long are the sessions and how many would you be doing in a day?
If you haven't done track time without the rotor on the crank I definately recommend trying it. I absolutely love the way the engine spins up with that weight removed.