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flywheel balance

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I work in a machine shop and we have a CNC lathe, I was planning on turning down my flywheel, but I know with cars and road bikes you have to balance them, or you can put stress on other parts and in some cases even lose power. Is that still the case with these little motors? I would imagine i should be save with just using the lathe sence its a [small] dirtbike. Anyone done it themselves?

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Ya, some do it themselves, but I would send it off to Procycle and have it lightened and balanced, and get a new gasket for just $45. Give yourself a break, and let them do it. Hope this helps. Thats what im going to do. They balance it for you.

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so it does need to be balanced. I think I'll just wait for my buddy to get his balancing thing ready, its for crank shafts but it does the same. why spend 45 smacks when i can do it for free. I walk by the equiptment like 50 times a day. but yea, we'll see

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Just my 2 cents worth: I just had mine turned down in our machine shop. We used an "inside chuck" to grab the flywheel from the inside. It seemed to spin smoother that way. Because we were taking steel off uniformly around the outer rim, the flywheel stayed just as balanced as ever. The motor runs great.

I have heard of folks removing material from crankshaft weights-this would be tough to do and still keep things balanced, but the machining of the outer part of the flywheel was no problem.

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Hey edwardsp,

What bike did you turn the fly wheel on ? How much did you take off ? Did it make a huge difference in the free reving and on the track/trail ?

Thanks

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It is a 125LE. According to what I've read, I took off about 14 ounces. I started to remove the starter gear and starter clutch. That would have been about as much weight as I had machined off. I backed out, left those parts in and stuck with the 14 ounces machined. I only got to ride in my TINY backyard for a few minutes, but I know it was quicker. I look forward to trying it out in the open or on a trail.

It turned out to be easier than I thought-the hardest part was getting the flywheel off.

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Did you lighten your piston to suit,or enhance the weight opposite the big end? simply reducing the flywheel weight will upset the throw and tend to create vibration. Timing of the ignition needs to change a tiny bit too.I made a set of wheels for my speedway bike and nearly done my head in with piston to wheel balance

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