Force 70 HP rebuild Wiseco piston ring gap question.

bullseye9899

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Aug 29, 2012
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I am rebuilding a Force 70 HP with a set of .040 over Wiseco pistons. After boring what method should I use to set the ring gap. The manual says .010 - .020 for the top ring and .006 - .016 for the bottom ring. This seemed a little on the side of alot of tolerance. The general method Wiseco suggest is .004 x inches in bore for the bottom and .005 x inches of bore for the top. That figured to be .014" and .017". This looks to be more inline to me. Not that I know anything about 2 strokes I'm more of a small block chevy builder. The bore is 3.514" if that helps. Thanks for any information or suggestions.
 

jerryjerry05

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Re: Force 70 HP rebuild Wiseco piston ring gap question.

Why so big on the pistons??
At .040 you might need to re-jet???
I'd go with the factory specs.
 

bullseye9899

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Re: Force 70 HP rebuild Wiseco piston ring gap question.

Had 2 burnt pistons one hole was pretty bad. The owner had ran it all summer on two cyl. #1 piston didn't even have rings anymore. .030 may have worked but they were out of stock anyway.
 

Frank Acampora

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Re: Force 70 HP rebuild Wiseco piston ring gap question.

Well, just be aware that older manuals recommended not boring more than .030. More than that and cylinder wall thickness becomes marginal. As far as ring gap Wiseco are usually very close to recommended tolerance IF the overbore is done correctly. 3.514 does not compute. Original bore was 3.375 --plus .040 equals 3.415. Did you transpose digits?

And I don't see your problem with ring gap. .014 and .017 is within the tolerances given in the manual. Even if you were to go to .020, that is only .003 over the computed .017---not significant.
 

bullseye9899

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Re: Force 70 HP rebuild Wiseco piston ring gap question.

Well, just be aware that older manuals recommended not boring more than .030. More than that and cylinder wall thickness becomes marginal. As far as ring gap Wiseco are usually very close to recommended tolerance IF the overbore is done correctly. 3.514 does not compute. Original bore was 3.375 --plus .040 equals 3.415. Did you transpose digits?

And I don't see your problem with ring gap. .014 and .017 is within the tolerances given in the manual. Even if you were to go to .020, that is only .003 over the computed .017---not significant.

Yes I did switch the numbers sorry.... The tolerances didn't worry me..... the fact that the gaps I had were very tight down to .008 and .010 did . I went back and we checked the piston clearance and it was correct .0053 I think. I called Wiesco and the tech said to open the gap to .014 on all the rings. The bore was pretty bad on 2 of the cyl. and I couldn't get .030 pistons so I went with the .040. Wish I had just waited until I found a set of .030 ...hopefully all will go well with it.
Thanks for the input.
 
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