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Benefits/downfalls of flywheel weights?

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My dad talked good about them. Although I don't even know how they work or what their good for. Can someone. Explain what they do and if their worth the price? I have a 96 yz250 2 stoke and am looking for anything to increase performance and making it a nice bike. What's your input and experience with them?

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My dad talked good about them. Although I don't even know how they work or what their good for. Can someone. Explain what they do and if their worth the price? I have a 96 yz250 2 stoke and am looking for anything to increase performance and making it a nice bike. What's your input and experience with them?

Technically speaking, flywheel weights are all about inertia, and intertia is about resisting change -- In this, case change in velocity. Adding a fww will add inertia to the engine, which will make it want to resist changing RPMs. It will rev up less quickly, and rev down less quickly. The more weight you add, the greater the effect. The benefits of this are that it tames the hit of the engine on acceleration, making the power roll on more smoothly, and likewise it will not let the engine slow down as quickly, which reduces stalling at low speeds and when braking. In general 2 strokes have relatively light internal moving parts (light flywheels, cranks, and no valvetrains) so they have a lot less inertia compared to 4 strokes. Adding a bit of additional rotating mass can make them easier to ride. From what I've read most people seem to like fww's on the 250.

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Technically speaking, flywheel weights are all about inertia, and intertia is about resisting change -- In this, case change in velocity. Adding a fww will add inertia to the engine, which will make it want to resist changing RPMs. It will rev up less quickly, and rev down less quickly. The more weight you add, the greater the effect. The benefits of this are that it tames the hit of the engine on acceleration, making the power roll on more smoothly, and likewise it will not let the engine slow down as quickly, which reduces stalling at low speeds and when braking. In general 2 strokes have relatively light internal moving parts (light flywheels, cranks, and no valvetrains) so they have a lot less inertia compared to 4 strokes. Adding a bit of additional rotating mass can make them easier to ride. From what I've read most people seem to like fww's on the 250.

Great explanation!
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I tried a flywheel weight on my 2010 YZ250.  I took it back off after a few rides as I didn't like how the inertia made the engine run on coming into corners.  I have retarded the timing 1 degree which has made it much more ridable in the bush/woods.

Edited by Gibbit
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