[68grandprix]

I just got new rings for my 1mm overbore 175 pistons. I checked the cylinder and piston with a digital caliper and got 52.9mm for the bore and 52.865mm for the piston. Does this sound good? Also, what should the ring end gap be? Thanks, Jimmy

 

[jbranson]

Jimmy,
That comes out to about .001" clearance...that's a bit too tight.
Make sure you measure the piston on the skirt...below the wrist pin...perpendicular to the wrist pin. (long side of the skirt to long side of the skirt).
Takes some practice to get repeatable measurements.

If you haven't had the cylinders bored.....that tight clearance could have been the reason the previous rings failed.

Measure carefully again...and if the numbers are still the same you need to consider something to open the cylinders up .001-.002 more. You could probably take it to a local shop and just have it honed out a thou or so. Don't take it to any idiot backyard shops...have it done by a competent bike or auto machine shop.

Ring end gap can be anywhere from about .006" to .030"....you do NOT want it smaller than .006" or the rings will bind up when the engine gets hot.
JohnnyB

 

[jbranson]

Jimmy,
That comes out to about .001" clearance...that's a bit too tight.
Make sure you measure the piston on the skirt...below the wrist pin...perpendicular to the wrist pin. (long side of the skirt to long side of the skirt).
Takes some practice to get repeatable measurements.

If you haven't had the cylinders bored.....that tight clearance could have been the reason the previous rings failed.

Measure carefully again...and if the numbers are still the same you need to consider something to open the cylinders up .001-.002 more. You could probably take it to a local shop and just have it honed out a thou or so. Don't take it to any idiot backyard shops...have it done by a competent bike or auto machine shop.

Ring end gap can be anywhere from about .006" to .030"....you do NOT want it smaller than .006" or the rings will bind up when the engine gets hot.
JohnnyB