Two Stroke Motocross
Two Stroke Motocross Forum => Technical => Topic started by: evo550 on December 04, 2010, 09:52:51 PM
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It's time for a top end freshen up. I can do the rebuild myself but I need to know what size piston to order (66.34,5 or 6mm), the piston in it is measuring as little as 66.22. So that really doesn't give me any indication.Does anyone know what clearance is required between cylinder and piston?
Also where is the best place to measure the cylinder?
Cheers Big Ears.
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About .06mm is a good clearance number though a little more is acceptable.Measure the piston 90 deg to the pin about 20 mm up on the skirt.Take measurements of the bore in various places to judge your taper but about 1/2 way down 90 deg to where the pin would be to judge clearance for the new piston.
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Also where is the best place to measure the cylinder?
Cheers Big Ears.
And here I was thinkin' you where going to say something like " In the garage" ;D
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They are quoting the piston size not the bore, as is European practice 66.22 + 0.06=66.28 for a 66.4mm(??) bore. Even if it was 0.08mm that still only takes you to 66.30mm.
The place to measure the bore is as close to the top of the exhaust port as possible
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Also where is the best place to measure the cylinder?
Cheers Big Ears.
And here I was thinkin' you where going to say something like " In the garage" ;D
Dammit,I missed a perfect opportunity-D'oh :D
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The place to measure the bore is as close to the top of the exhaust port as possible
Measuring at the very top will give original bore,measuring at the bottom will give measure of least wear.Measuring at the top of the ex ports will give a high wear area.If you order your piston by this spec you'll be too tight on the bottom.