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Old 07-12-2011, 12:13 AM
ed_563's Avatar
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Default piston/cylinder clearance 2000 cr250r

2000 cr250r

Bike runs great, no engine noise or anything, lots of power, compression tested around 180psi a month or so ago. (havnt ridden it much since, maybe 6 hours)

I bough the bike from my buddie last year. He owned it previously for 5 years or so.
I decided to put a new piston in it, 6 years seemed a little past due.

I pulled out the old piston, looked in great shape. Same with the rings.
But i noticed there is excessive piston to cylinder wall clearance between the intake and exhaust 'Y' axis.

There is probably a millimeter maybe oven more of slop when u set the new piston in there (without the rings on)

The side to side 'x' axis clearance seems good and tight.

The service manual says the service limit for piston to wall clearance is 0.09mm. If that is the case, wouldnt i have been hearing piston slap when the bike is running?
The old piston shows very very little to almost no piston slap wear.

What do i do? Hone the cylinder, throw the new piston in, and run it?
Or should i bore the old nikasil, and put a sleeve in it?

My buddy is a journymen deisel engine mechanic, he says cylinders and pistons are suppose to be a slight oval shape for heat expansion reasons.

maybe i am worrying too much, and my cylinder is normal.

Is this suppose to be like this?
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Old 07-12-2011, 05:34 AM
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As time go's on cylinders will get out of round. I just had my 05 cr125 cylinder micd out and it was only a half a thousanths out of round. Yours sounds like it needs to be re done
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Old 07-12-2011, 10:52 AM
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Clearance is measured at or near the end of the skirt. Not the head.
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Old 07-12-2011, 01:36 PM
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Quote:
Originally Posted by ossagp View Post
Clearance is measured at or near the end of the skirt. Not the head.
touche!


so, i should put the cylinder in upside down and have a look

Last edited by ed_563; 07-12-2011 at 01:38 PM. Reason: typo
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