- Joined
- Jun 30, 2012
- Messages
- 13,275
The torque output of the motor depends on many things. A two into one pipe is restrictive, however if the exhaust valve opens earlier to compensate, a better result can be achieved. With the 850, I advance the cam by 12 degrees, This means the inlet opens at about 65 BTDC, and the exhaust at about 94 BBDC - which is theoretically too early. My bike is too loud, however I have a 2S combat cam which only has to be advanced by 6 degrees to get similar inlet opening, and the exhaust opening should be much better. (LOUD is an indication of lost power)
The problem is that if you improve the torque characteristic, the bike does not accelerate any faster unless you raise the overall gearing. And short-shifting often does not help the acceleration as the gaps between gears are usually too large. The close box allows you to ride the top of the torque curve to get the best acceleration. The top end horsepower is pretty much irrelevant if the motor has little midrange. If you've ever ridden a racing two stroke into a head-wind - the almost stop as soon as the revs start to drop.
The problem is that if you improve the torque characteristic, the bike does not accelerate any faster unless you raise the overall gearing. And short-shifting often does not help the acceleration as the gaps between gears are usually too large. The close box allows you to ride the top of the torque curve to get the best acceleration. The top end horsepower is pretty much irrelevant if the motor has little midrange. If you've ever ridden a racing two stroke into a head-wind - the almost stop as soon as the revs start to drop.