Dave, I have a 2 yr old YS 110 with very little run time on it. Last winter, shortly after taking off the muffler fell off and I dead sticked it in. I recently tried to use it (with a new Muffler) and it seems to have very little compression (You can feel a little, but I can easily spin the prop with one finger)

Anything I should check, or should I just send it in?

Valves stuck, rings stuck? Pull the valve cover off, and make sure the valves move when turning the prop. Then, I would fill the tank, REMOVE THE GLOW PLUG and spin it up with the starter for a couple minutes. Be sure to do this at full throttle.

Put the plug back in and proceed as in a normal start up at low throttle. Bet the compression comes back.

Sorry, I should have mentioned that the valves worked fine and the rocker arms had proper clearance.

I'll try your suggestion and report back. Thanks

Let me know, thanks.