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Flywheel

Old 02-29-2008, 05:35 AM
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Flywheel

I looked forthis topic, butdidn't get too much.

How many people have cut there flywheel down? How much are you cutting off the flywheel, and how much difference does it make?


I just got done machining a flywheel for a 1980 yamaha 440srx. I machined it to the 1977 spec for the same sled, so I had some type of baseline and an expectation of what to expect as far as running condition. I have also worked with cars in the lightened flywheel arena and have heard of problems with duc 916's. I am worried that I may have hard starting or running issues. Someone tell me otherwise, cause I wanna go fast.
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Old 02-29-2008, 05:57 AM
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Was doing a search may be you could ask him how it tured out.

https://www.superhawkforum.com/forum...light=flywheel

Stumpy.
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Old 02-29-2008, 06:18 AM
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You can also try e-mailing Roger Ditchfield at Revolution Racing in the UK. He can give you the exact specs he developed when doing development work on the VTR for HRC. I got him to machine one for me (do not necessarily recommend going this route due to shipping costs) and it works real nice.
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Old 02-29-2008, 10:37 AM
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I've talked about this a bunch of times. I'm sure everyone's sick of it, but here goes again.

After much testing, not done by me, it was found that 1/2 inch off the diameter worked fine. that's what Moriwaki did. That's what i did, and it worked fine for me too.

Twins like flywheel, but you will still have plenty. On track days, you have to crack the throttle, to keep from locking the rear wheel when downshifting. No big deal. Everybody without a slipper clutch has to do it. On high HP engines, a light flywheel can also lead to spinning the rear tire on acceleration. But that's with a highly modified engine with a lightened crank and rods.

My friend Bob talked to Colin Edwards about this and he agreed that too little flywheel is not good for putting power to the ground. But that's at the superbike level.

Take 1/2 inch off the diameter. It works fine. You won't notice any trouble riding around town, starting, idling. For street riding there's no trouble with downshifting.

No problems.
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Old 02-29-2008, 10:44 AM
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Also...

the RC51 flywheel is much lighter than VTR1000F flywheel. I don't have a picture of an RC51 flywheel, but I've worked on both.
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Old 02-29-2008, 03:43 PM
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I can't say for sure how much difference you will feel. The crankshaft has the widest RPM range of any shaft on the motorcycle, and spans that range more quickly and frequently than anything else. 1/2" off the diameter is a huge change in flywheel inertia. It's like Honda was afraid this motorcycle was going to be trouble in the hands of the inexperienced and gave it lots of inertia, undersprung the front end, oversprung the rear end and wanted to keep the front end on the ground. The VTR was basically an engine testbed for the RC51 superbike effort.

Sorry if I always sound like I think I know everything about these things. I certainly don't. But I do know that I had some of the best information available. Just passing it along.
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