Can someone tell me what the pros and cons to lightening a
flywheel are and how much you lighten it? I have been told
you should not do this without welding your crank first, is
that true? Is this practical to do with a big bore motor and/or
long rod motor?

 

I had mine lightened by Power Playground Racing in Kansas. I wasn't really sure i'd even like it. But I do. I haven't had the crank trued but it is welded. Not sure that it's absolutely necessary, I just knew someone that could do it so I had it done. It seems to be more responsive is the main difference I noticed. I thought it would require more shifting by chance but it doesn't. The best part is how it powers out of spots, like corners especially if you have any traction. If you come out of a tacky corner like on a track hang on. I've had some other stuff done to mine though. With what i've had done the bottom end is really great on this thing now. Have friend that MX's and he loves it too.

 

lightening isnt allways the answer,the type of riding that you do should dictate this,lighter is more for drag racing,a heavyier flywheel works great in the woods,,check it all out first [img]i/expressions/face-icon-small-smile.gif[/img]

 

I believe that any rotating mass that you can lighten without weaking something too far has positive effects. Lighter rotating mass doesn't decrease low end. It increases rear wheel HP. The less energy it takes to turn enternal components the more power you will have out the output shaft. Yes it will rev quicker but, how will this take away from torque?
I had mine lightened from TC. The original is just over 5.5 pounds and mine is at 4.75lbs. I am having another one done and mine also cut on some more. I would at least like one full pound off mine, we will see.
Hope this helps. (That is a 400ex by the way).

 

Leaving a flywheel alone or actually adding weight helps to keep the motor from stalling. That's why alot of woods racers have heavier flywheels.

 

by lightening your flywheel your engine will have to turn less mass making it rev quicker now the down fall is that with less weight you will lose your revs that much faster.So for draging it's a good thing for moto-x and trials when you want to keep the revs up for when your coming out of a corner i don't think that it's the best idea,but some companys take different amounts off depending on what type of riding that you do-