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Old 08-27-2018, 09:25 AM
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Default Need help with 03 cr250 piston sizing

     

I could really use some help. I need to order a piston kit for my cr250 but I'm not sure what size to get. My bore size measures out to be 66.35mm. Pro-x lists there piston as

A. 66.34mm and B.66.35mm, are they referring to the piston size or bore size. The old piston out of it is a Pro-x B which I am changing as I was getting alot of noise, when I took it out it kinda seemed too move in the bore way too much.
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Old 08-28-2018, 04:11 PM
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Sorry I cannot answer question,but my sugestion is to contact
Prox if you gonna go that brand again.
Measure old piston riht above piston pin on side
What does it measure?
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Old 08-29-2018, 05:25 AM
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Quote:
Originally Posted by OlSchoolFool393 View Post
Sorry I cannot answer question,but my sugestion is to contact
Prox if you gonna go that brand again.
Measure old piston riht above piston pin on side
What does it measure?
Last night, most of the confusion got resolved. I just figured out that my micrometer needed calibrating. My exact bore size is 2.6142 (66.40). The Honda service manual shows that measurement as an 'A' cylinder but my cylinder is marked 'B'. I can make sense of this as its been re coated recently. The part that is strange to me is Pro-x lists there 'A' piston as being smaller than there 'B' piston, where as Honda listed there 'B' piston as being the smaller of the two. This is kind of messed up as I thought Pro-x was the OEM piston manufacturer for Honda. As long as all my measurements are correct, I am going to put a pro-x 'B' piston in it and get just over .002 clearance
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Old 08-31-2018, 04:49 AM
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Did you measure with a bore gauge? The cylinder should be measured in six places and averaged. I would be absolutely sure of your measurements before running a "B" piston in an "A" cylinder. You can't properly measure a cylinder with a micrometer.
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Old 09-04-2018, 07:29 AM
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Replate it get a stock piston.
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