| You will get more engine braking with less interia on the crank.
Think of it this way. With the engine at a high RPM, the inertia of the flywheel (or any other inertia in the drive train, such as the clutch) will want to keep the engine spinning as you close the throttle. The engine needs to absorb the energy stored in the flywheel.
So, as you reduce the inertia of the drive train, e.g. lighter flywheel, lighter clutch assembly, the engine will slow down quicker since there is less inertia trying to keep it spinning, hence more engine braking.
The downside of lighter flywheels and clutch, as pointed out already by some people, is the effect on idle. The inertia of the flywheel tends to smooth out the idle. Take away the inertia and your idle becomes lumpy. You may even need to increase the idle speed to keep it from stalling.
I run a very light flywheel and clutch and it makes for a great performing engine, but the idle is very poor. This is amplified by the particular throttle bodies, so mine may not be a good example of what you find with a street bike. I know of quite a few people that run lighter flywheels and they have almost no negative side effects. It will almost definitely make want to install a slipper clutch due to the increase in engine braking.  |