cr 125 what size drill bit for oil holes

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showstopper11

New member
what size drill bit do you guys use to drill the oil lube holes in the piston for the exhaust bridge on the piston. wiseco says .60-.090" diameter it is in a cr125 do you guys even recommend it?
 
showstopper11 said:
the engine is ran at full rpms they say it helps the cooling / lube on the bridge on the exaust side
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Yeh i know it helps with lube, I'm just saying any size hole that wiseco recommends will be Ok. If you nip up on the bridge then you got problems that most likely cant be fixed with extra lubrication. Would be more like some sort of expansion or clearance issue if you had problems on the exh bridge.
 
I’m no expert for sure, but the pistons I’ve seen had much smaller holes. At least half that size. And the ones I’ve seen had two or three of these small holes. Just guessing but as I remember it, the holes where smaller than .032”. I’ll bet Pete Muller would know what works best.
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.090 seems a bit bigger than necessary, we always used about .046 and did three of them, it wouldn't hurt to relieve the bridge a little also, that bridge gets so hot it's gonna expand some. Jon
 
not a cr specific answer but i always did it on my bikes by assembling engine without holes in piston (no wrist pin clips) spraying dry moly lube up the exhaust port to mark the bridge location, then drilling about half the width of that down the center with 3 holes. fwiw.
 
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