Piston Rings.....
Discussion
Hi -
while re-assembling an old JAP 2 stroke, I managed to snap one of the (2) piston rings...
I cannot find a replacement anywhere. The rings measure 45mm x 2mm x 2mm. On feebay there are some for a different motor for sale. But they measure 45mm x 1.95mm high x 1.85mm wide.
Do you reckon I can get away with these? or will that slight undersizing allow the ring to shake and cut up the bore..? The motor wont be run hard - just a stationary motor with little loading... Luckily the height is almost spot on, on;y 2 thou out... and the 6 thou on the width could potentially (maybe?) be the same as a badly worn ring???!????
while re-assembling an old JAP 2 stroke, I managed to snap one of the (2) piston rings...
I cannot find a replacement anywhere. The rings measure 45mm x 2mm x 2mm. On feebay there are some for a different motor for sale. But they measure 45mm x 1.95mm high x 1.85mm wide.
Do you reckon I can get away with these? or will that slight undersizing allow the ring to shake and cut up the bore..? The motor wont be run hard - just a stationary motor with little loading... Luckily the height is almost spot on, on;y 2 thou out... and the 6 thou on the width could potentially (maybe?) be the same as a badly worn ring???!????
OP, as Stevie says, Dave should be able to get you something. He'll want to know the width, depth and height of your ring grooves. Also, you may find it cheaper to order a set as opposed to one ring.
Have you tried Gaggs?
http://www.gagg-and-sons.freeserve.co.uk/main.html
A phone call to them may be helpful. They've been around for eons.
Have you tried Gaggs?
http://www.gagg-and-sons.freeserve.co.uk/main.html
A phone call to them may be helpful. They've been around for eons.
You seem to have a few misconceptions about how piston ring sizing works.
The nominal ring vertical thickness is the groove width it is meant to fit into. The ring itself will be 2 thou thinner because that's the clearance needed. A 1.95mm thick ring is obviously meant for a 2mm groove, or just possibly a 5/64" groove but it will interchange.
The ring radial depth is fairly immaterial as long as the ring doesn't bottom out in the groove. A few thou thou thinner than OE is neither here nor there.
The only other concern on a 2 stroke is the diameter of the peg that the rings fit round to stop them rotating. However rings usually have a cutout ground in the ends that is large enough to cope with small variations in peg size.
The Ebay rings you found are very likely perfectly fine.
The nominal ring vertical thickness is the groove width it is meant to fit into. The ring itself will be 2 thou thinner because that's the clearance needed. A 1.95mm thick ring is obviously meant for a 2mm groove, or just possibly a 5/64" groove but it will interchange.
The ring radial depth is fairly immaterial as long as the ring doesn't bottom out in the groove. A few thou thou thinner than OE is neither here nor there.
The only other concern on a 2 stroke is the diameter of the peg that the rings fit round to stop them rotating. However rings usually have a cutout ground in the ends that is large enough to cope with small variations in peg size.
The Ebay rings you found are very likely perfectly fine.
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