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flywheel weights

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hey....ive seen a lot of guys saying to get a motocross bike, and put a flywheel weight on it. whats the purpose of this?? i could see lightening it to make it rev faster...but why would anyone want a slower revving bike?? why not just get a trail bike? i think ive seen someone with a crf450 and a 31 oz flywheel weight...why not just get say a xr 400....your thoughts??? :cry:

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The flywheel keeps the engine rotating smoothly, especially at low rpm, keeps it from stalling. At higher revs, the weight of the flywheel slows the speed at which the motor can rev, making it more tractable.

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yeah, 31 oz seems a little extreme to me, especially on a 4-stroke (all 4-strokes seem slow revving and tractable to me, but i haven't ridden the yzf450). i put a 6oz weight on my 250sx, and it still revs insanely briskly, it's just a little more controllable now, and i get better traction in 1st and 2nd gear. stock, it was only useful on an mx track with fairly decent traction, but in the tight desert stuff around here it was challenging to not just dig a trench trying to go up slow hills.

if you want to seriously race offroad, you have traditionally had a few choices:

a) buy a trail bike (xr, kdx, klx, dr) and spend all your time and money trying to make the suspension work for fast riding and trying to give the motor enough power to get out of it's own way.

:cry: buy a japanese mx bike and smooth out the power with a flywheel weight and gnarly pipe and have the suspension revalved for off-road.

c) buy a ktm.

if ktm (and gasgas) weren't making some serious high-performance enduro/desert bikes, it would certainly make the most sense to convert an mx bike for offroad racing, since it's cheaper and easier to tame an mx bike than it is to hop up a trailbike for racing.

keep in mind that a modern mx bike with a reasonable flywheel weight will still rev fast enough that you have to have some skill to control it in 1st and 2nd gear. it's just a little easier to do that when you're tired and in low-traction (sand, mud) conditions.

mw

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