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ktmheinzee

1998 yz400f flywheel

7 posts in this topic

I just pass down my bike to my son and want to make it easier to ride at low speeds since that what we ride. The bike was designed for supercross/motorcross and stalls during low idle riding... Question has anyone changed to a heavier flywheel? If so what weight/brand and how are the results, and how was the install?

Thanks

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I have a 426 and went to a 12 oz Ty Davis. I absolutely love it. Hardly lost any punch and I can lug the hell out of it with no stalling. My brother liked it soo much, he put one on his CRF450 also and loves it.

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Does the flywheel make that much difference in the low end? I would naturaly just assume to turn up the idle to keep from stalling. I'm just curious why changing the flywheel would make a difference?

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At low speeds, the compression stroke tires to stop the engine every time it happens. Without the help of another cylinder or two to push the piston past that, the compression stroke, combines with any significant load on the engine, can cause a stall. A heavier flywheel adds additional rotational inertia to help keep the engine turning, and helps it run more smoothly at low rpm.

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I had the idle turned up on my bike and it made it a pain in the ass to ride at slow speeds when I wanted to.

More rotational mass on the flywheel gives the engine more of a tendency to keep spinning instead of stalling, but will seem to suck some power out of the engine because it takes more engine's power to spin the engine up. Alternatively, if you want your engine to spin up faster but don't need to lug the engine at all, put a lighter flywheel on it.

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More rotational mass on the flywheel gives the engine more of a tendency to keep spinning instead of stalling, but will seem to suck some power out of the engine because it takes more engine's power to spin the engine up.

I can pretty much promise you that you won't notice the power loss.

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Gray is the one that reccomended the flywheel weight for me and I absolutely would not change a thing. Just wish I would of done it alot sooner. Did not notice power loss !

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