OS91 4 Stroke Compession
I acquired from a friend a older OS 91 4 stroke. When I turn the prop by hand or starter there is no compression. It won't start unless I use a starter and put my finger over the muffler opening to get it started. Once I have done that it seems to run fine, power seems to OK.
When I shut the engine off still no compression, if I put the starter back on the engine immediately it starts right up without putting my thumb or finger over the muffler opening. The valves are in adjustment, the liner looks OK, and the bearings seem to be smooth.
Any suggestions what could be wrong?