Could you be more specific, please? Nice post.Lightened flywheels are a great source of "free" power in that not only is "power" (defined broadly") increased, but also economy is increased.
Still, some drivers insist and perhaps correctly that a heavy flywheel is good for drag racing in that its mass decreases bogging at the start line.
As for "chatter", gears do not chatter when engaged. The "chatter" referenced is usually seen when the gearbox is in neutral and motor impulses not dampened by the flywheel cause the loose gears to vibrate=chatter.
The concept of "mass" is not well understood. Mass = the weight of the object X the square of the speed. A flywheel spinning at redline has a huge amount of mass, whereas contrasted a wheel weighing roughly the same has much less mass because through gearing its rotational speed is much less.
UUC's comments are well written. Below is another source. Graham Bell is a Brit who has been writing rather well about motors for many years.
Graham Bell in his book Four Stroke Performance Tuning writes:
“Over the years there ahas been a fair amount of controversy with regard to flywheel lightening. Some claimed that a lightweight flywheel improved acceleration due to reduced inertia, others stated that the only benefit was better crankshaft life because the twisting load on the end of the crank was reduced, and there was less risk of flywheel explosion due to inertia load on the centre of the flywheel being lessened. At this time we can state and prove that any reductions in an engine’s reciprocating mass or rotating mass will improve acceleration. Thus lightweight pistons, rods, cranks, clutches and flywheels all benefit performance.
The problem was that we had no reliable means of measuring the performance advantages of light components. However, the situation changed when relatively inexpensive computerised engine dynos like the Superflow SF-800 became available. These dynos can accelerate an engine at a fixed rate and accurately print out the horsepower on a tape. This means that we can programme the dyno to accelerate the engine at, say, 2000 rpm per second, and record the power levels every 250-rpm. When such a test was carried out on a 388 cu. in. Chev speedway engine, it recorded almost 25 hp more when titanium rods and a light flywheel were fitted. The driver claimed that the car was quicker by about a half-length out of turns, which backed up what the dyno had showed. Tested with a static load as we had to with the older dynos, the engine showed no difference in hp when the lightweight parts were fitted.”