i am a bit confused. I am measuring my piston skirts and cylinder diameter. My cylinder diameter is looking to be about 2.9504” and when I measure my piston skirt I am getting about 2.9502. This doesn’t seem right as I thought piston clearance should be about .002 and I am off by a factor of 10. Any thoughts on what I’m doin wrong? I haven’t honed the cylinder yet I was really just trying my new micrometer out. After I hone would this correct the clearance? or is it my technique? I followed the video jim made on measuring cylinders and have been getting consistency. I measured the skirt at the lowest part of the piston.
-
Enjoy XS650.com? Consider making a donation to help support the site.
XS650.com receives a small share of sales from some links on this page, but direct donations have a much greater impact on keeping this site going.
Piston skirt clearance seems off
- Thread starter JE4570
- Start date
You usually measure the skirt 1/2" to 3/4" up from the bottom, not at the lowest point or very bottom. How are your measurements comparing to the original sizes? The original sizes should be marked on the pistons and on the outside of the sleeve that sticks out of the bottom of the cylinder casting. Obviously, if anything, you usually find the piston worn smaller and the bore worn bigger.
You're reporting values down to the tenths of a thou. A delicate area, requiring sensitive touch, and interpretation of the micrometer's vernier scale. Maybe pics of your micrometer readings may help...
Myself, I prefer the feeler gauge method. It's a direct measurement, rather than a computed/derived measurement from different measurements that have their own individual errors.
Something else to consider. A 3" XS650 piston, sitting on the bench at 60°F, will swell 25 microns (0.001") after you've held it in your hand awhile, and it's now warmed-up to 85°F. An expansion variation of about 1 micron per degree F.
Something else to consider. A 3" XS650 piston, sitting on the bench at 60°F, will swell 25 microns (0.001") after you've held it in your hand awhile, and it's now warmed-up to 85°F. An expansion variation of about 1 micron per degree F.
