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What is the benefit to adding fly wheel weight

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What is the benefit of adding additional weight to the fly wheel, what changes does it do the way the engine power is delevered.

I have big bore RM250 and its been recommended to add weight to the fly wheel?

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Basically, the more weight rotating with the flywheel the more torque you will create but this is offset by the power used to start its rotation.

This is why say for an MX bike, in most cases you would not use extra flywheel weight as you want the bike to rev up and down quickly.

On a bike for woods use where you are on/off the throttle over technical terrain, extra weight can be added to the flywheel so that once it is spinning it will retain more kinetic energy creating smoother and more tractable power delivery.

Hope this makes some sense.

Edited by dirtynidge
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depends what you want, more weight if you want like 4 stroke power

i have a 8 oz on my 06rm250 and i love it, still has a hit but is smoothed out a bit down low to mid

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I agree with the above replies except for one thing - some very good mx'ers use will use a lighter FWW. While there are plenty of voices for a weight for woods riding, I learned directly from an "A" mx rider that a FWW helped him most out of corners and when it got slippery.

You would loose a little KAPOW on a short run before a jump but the right amount of clutch compensates and you gotta pretty much use some clutch anyway. So for a good mx rider that's got their controls skills down the FWW actually gives them an edge. And he knew a few other racers that had them.

I bought the heaviest weight (13 oz) pretty much right after I bought my 250 because I wanted to maximize traction in woods/offroad. I was a little worried that the 13oz might dull the hit too much but, for me, it turned out to be just fine because these 250s have PLENTY of power and the thing STILL lights off . . . but in a controlled fashion.

I should say that I have carburetor and head mods so I'm not stock . . . but that is more like what you've got with a big bore (although I'd like to get a big bore myself, so I'm interested in hearing your thoughts about that)

One more thing . . . if you go for the weight, whatever size you pick remember that you could resell it and get most $ back to move to a different size because there's nothing that wears.

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Some very good explanations here, thanks, it was 13 onz recommended.

What the weight look like and how is it attached tot he fly wheel or do you buy a hevier fly wheel.

Edited by motolink

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Some very good explaations here, thnaks, it was 13 onz recommended.

What the weight look like and how is it attached tot he fly wheel or do you buy a hevier fly wheel.

It's attached to the existing flywheel. I don't know if other years' RMs are different, but on mine the flywheel weight was threaded in the mounting hole, so effectively it replaced the stock flywheel weight nut.

When you buy one you should get instructions with it, pretty self-explanatory.

The steel vs. plastic merry-go-round is a very clever analogy. Stored energy is what it's all about.

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Well that all makes sence.

There was a FWW that had a base (6 oz) with two rings (2oz ea). You could have a 6, 8 & 10 oz weight. Took 10 min. to go from a 6 oz to a 10 oz if you needed it for the mud or hill clinbs.....

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I did see a 13onz weight on the net for sale by SFB for sale, what is around the right price.

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Here is a yz250 weight from GYTR. Read the "note" section and it explains the importance of the added weight location. (I know its for a yz, but it makes sense). I would stay away from the bolt on rings. Never heard of an issue, but you never know! I run a weight on my 450 for mx only. It's only 6oz, but it helped. For the woods a weight is a must!

http://www.yamaha-motor.com/sport/accessories/acscitemdetail/5/30/11/2286/all/2/3320/0/detail.aspx

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crfoot, that is a good article, where would I get a full fly wheel for a RM250.

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I did see a 13onz weight on the net for sale by SFB for sale, what is around the right price.

It sold for $70.00, looked like good value.

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After adding weight is it easy to feel and pick the difference.

Yes ,,that's a good way of putting it...You can feel and pick the difference....I use a 10oz'er..it's just right for moto and the trail's....Dr.D....

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