Shaft size and clutch fitment question

greaser_monkey_87

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Mar 30, 2014
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My current engine has a 16mm shaft, and the clutch was originally for a 5/8 shaft but I had it bored out to fit my shaft. I'm seriously considering a Predator engine, which has a 5/8 shaft. The difference between 5/8 and 16mm is 0.125mm. Can I use the clutch I have the way it is, or should I get a new backing plate to fit the 5/8 shaft.
 

Greg58

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May 1, 2011
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I would get a new plate, the amount cut out will cause a offset of center and the chain will pulse in relation to the offset. I don't think the risk of damaging the output shaft is worth it.
 

silvaire

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Jan 25, 2009
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I agree with Greg58 to some degree. A difference in diameters of 0.125mm is just under .005" - likely enough to feel a little pulsing depending on how tight the chain is. The more significant concern is possibly doing damage your clutch hub and/or crankshaft with the wobbling loose fit on the shaft if you run it this way for very long.

I would suggest trying some .002" brass or stainless shim stock to fill the gap as a temporary measure, and see how the project works out before investing in a new hub though.
 
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greaser_monkey_87

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Mar 30, 2014
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I decided to decommission my current bike as a motored ride. Since my wife is getting a tuition reimbursement check from her online school, I have two whole paychecks to spend on bike parts. I'm just going to buy a new bike.
 

greaser_monkey_87

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Mar 30, 2014
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After looking at the Predator shaft and fitting the 16mm clutch up to it, I can't see why it would be a problem. There is a lot more than 0.125mm play in the drum, so the bore difference in the clutch hub is unlikely to have any effect on the crankshaft or the chain. I'm going to save myself $35 and use this clutch.