Suprise after top end removal.

[brveagle]

Glad Cafe Racer took care of you... Greg and Dan are good guys



-local KC guy...

[niclpnut]

Glad Cafe Racer took care of you... Greg and Dan are good guys



-local KC guy...

Yup.

Good people there. And Jim over at Cyclops in Shawnee. Always willing to answer my dumb questions


Nic

[Normk]

Nic, not sure if you have the measurement questions answered to your staisfaction?

Piston to cylinder wall clearance should be measured towards the bottom of the skirt as someone pointed out. Clearance at the top of the piston and in particular above the compression ring land is almost meaningless.

If using a feeler guage, which is how this has typically been done very accurately for a century, is performed by slipping a long feeler guage against the "side" of the cylinder wall at 90 degrees to the crankshaft, then sliding the piston in against the feeler.

The feeler will be able to be withdrawn subject to a light drag if the clearance is equal to the thickness of the feeler. On motorcycle and other small diameter pistons it can be useful to utilize a long narrow feeler guage rather than a standard width feeler.

A feeler guage will provide accurate clearance in the hands of someone who is advised. The alternative, use of an inside mic or cylinder bore guage compared against that of an outside mic of the piston is a more difficult means to almost the same end. While it may seem that the micrometers or micrometer and bore guage method must be more accurate, consider that this method introduces to variability issues rather than a single one.

I prefer the use of a feeler for checking piston clearance even though I prefer an inside mic or bore guage for checking out of round and taper.

Another useful lesson is that of always checking piston clearance at several points after a re-bore. We once received an engine back from boring which had more than 12 thou" of cylinder taper....but let's not go there!

Piston to cylinder wall clearace (as long is it isn't too little) is not a huge issue or at least not to the degree of excessive cylinder taper or out of round. I have knurled pistons in dozens of engines to correct a bit of excess piston clearance with the engines often lasting longer than from new.

HIH

Norm