Got an xl400 on ebay awhile back. Its a good looking saw that starts good but is a little short on grunt, not alot short but alittle. Today I had the muf off to change an oil line and gave piston a quick look and what to my wondering eyes should appear..... the piston only has one ring on it. This baffles me because the p/c look perfect and the compression is 150 at 4 or 5 pulls. So the question is how the hell did the ring come off and not destroy things, and if it was never put on to begin with why the heck would anyone do that. It is the ring closest to the spark plug. I guess the good news is that when i get a second ring on her she'll be a beast. Bad news is its not a carb problem. Any thoughts other than, (thats whatcha get for saw shoppin on ebay)