piston/bore clearance? tolerance too much??

blsnelling said:

Bore's aren't tapered, but the pistons are. Measure the piston at the very bottom of the skirts. .020" is WAAAY too much. Should be more like .003".

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blsnelling said:

Bore's aren't tapered, but the pistons are. Measure the piston at the very bottom of the skirts. .020" is WAAAY too much. Should be more like .003".

Click to expand...

SawGarage said:

Hey guys!!

I have a jonsered 670 i'm working on...

saw seized a ring with the #1 piston...dealer installed the top end not long before it failed... your THOUGHTS????

i have the orig piston that came out of it (piston 1) and another on a parts saw (piston 2)...

cyl is in good shape, and the bore is ~50.03mm

I have .020" clearance with the #1 piston and the cyl....seems like a lot?!?:help:

I put the (#1) piston in, sans ring, and it rattles around in the bore a bit more than i think it should....

piston #1 measures: 49.26mm 1/4 of the way up the skirt from bottom front to back (intake to exhaust side)
49.05mm Intake to Exhaust
49.33mm perpendicular to the ports

piston #2 measures: 49.65mm 1/4 up
49.50mm I-E
49.60mm perpendicular..

both are in good shape, with only the slightest wear marks... i'm thinking #1 is scrap, and #2 may be useable???

Thoughts??

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blsnelling said:

Bore's aren't tapered, but the pistons are. Measure the piston at the very bottom of the skirts. .020" is WAAAY too much. Should be more like .003".

Click to expand...

lone wolf said:

since when do the set them up at that size unless something has changed dramatically I would say wrong piston maybe look into that.

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