[jct842]

When I was a kid I had a james motorcycle that had a very worn villiars engine in it. At the bottom of the stroke you could wiggle the piston sideways about an 1/8th of an inch. I used to replace rings with some for a briggs engine every 2 or 3 weeks.

At the top of the stroke there will be a ridge that has to be removed if it is there. Then as mentioned a ring can catch on a port. Also the ring gap has to be right. Put the ring in the cyl, use the piston to get it square and then put a feeler gauge in the gap. measure at the top of cyl and at the bottom where it would be if it was in the piston. Your manufacturer will have the numbers to go by, If the gap is too large the cyl would need either replacing or boring. If it is too tight you may have the wrong size rings. They can be filed if it is only a few thousands. And there are better instructions on the internet for doing this.