Accelerating and Shifting

In physics, acceleration is the rate of change of velocity with respect to time. Torque is defined as the force that produces rotation about an axis. Thus, engine torque is the measurement of the power that creates different RPM. Shifting is how you keep the engine operating in the useful torque range. You must have a "feel" for the torque curve of the motorcycle for efficient and effective accelerating and shifting.

Acceleration from a dead stop requires coordinating the transfer of power from the engine, through the clutch, to the drive train and rear wheel. Too much throttle with too much clutch may cause the bike to jump or the rear tire to spin out. Too much engine with too little clutch will burn out the clutch. Too little engine with too much clutch will often cause the engine to stall. Incorrect acceleration of any type is very hard on the engine and drive train. Control the flow of power by balancing the engine's RPMs with the degree to which the clutch is engaged. Keep the throttle even, increasing the throttle as the clutch engages.

In general, you want to shift so that you keep the engine's speed high on the ascending side of the torque curve. This is the engine's "sweet spot." This is where there is a good deal of available power at both lower and higher RPMs. If you are running at an engine speed where you still have power for powering out of a bad situation, but also have power if you lose a thousand r.p.m. or two, you are running in the engine's "sweet spot."

Everyone has their own idea of when to shift up and down. Upshifting too early (i.e., at too low a rate of RPM) "lugs" the engine and contributes to overheated valves. Upshifting too late wastes fuel. Upshifting way too late can cause major engine damage (e.g., thrown rods, scored bearings, busted gear teeth) if RPMs reach redline. Within these guidelines rests most of the tachometer and torque curve, so you should never commit these sins.

Downshifting is a bit trickier than upshifting because the throttle action is different. When downshifting, you actually increase the throttle as you release the clutch so not to subject the drive train and engine to a power surge from the rear wheel. This power surge can cause massive bearing failure in large mass engines (mostly older European and American bikes). It is for this reason that downshift points are at lower r.p.m.s than upshift points. For example, you might upshift into fifth at 3,000 r.p.m., but downshift out of fifth at 2,000 r.p.m.