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I'm installing a new .20 over Wiseco piston in my 2005 660 project, and have a couple questions about the fit.

I had the cylinder bored, and checked the piston clearance, and got .0023.
The factory spec is .0022 to .0028, and the Wiseco box says .0025 clearance, and doesn't give a range.
So I'm just inside the factory spec, but tight according to the Wiseco box. Will this be OK, or do I need to increase the bore?

Also checking the ring end gaps, I'm getting just over .012 on both the top and second rings.
The factory spec is .0118 to .0177.
The Wiseco instructions give a calculation of Bore X .004 for top ring, and Bore X .0050 for second ring.
This came out to be .0158 for the top ring, and .0198 for the second ring.
The Wiseco instructions also mention the end gap on the second ring should be larger than that of the top ring.
Again, I'm just inside the factory spec, but tighter than the Wiseco number. Also my top and second ring end gaps are the same. Will this be OK?
 

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I recently installed a new JE piston in my 05' 660 raptor. Looking at your piston to cylinder clearance i think you are fine. As far as your rings i went with factory gaps. I would think you are good but im no expert. I am sure someone here will have some good advice for you. Its not to big a deal to file your rings down to the wiseco specs but i would think the tighter the better. Good luck=)
 

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Not an experianced builder but the specs differ because the stock piston and larger bore OEM Yamaha pistons are cast. The Wiseco is forged, and forged pistons require a larger clearance.
 
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