engine model is 251417-0159-01. Ususlly it will sputter but not start. Has good spark. Points magneto was replaced with the electronic version at some point. Now we can get it to start but not rev very high. Will not start with any amount of throttle at all. I usually get it to start by cranking and sloowwwllyyyy increasing throttle a bit from low throttle but not much. It has to be exactly in the sweet zone. Compression is all over the place. Ive seen 50, 60, 80, 105, 110. Took out valves, lapped them and adjusted clearance once reinstalled. Right at this point in time I think I can go out and start it but it wont rev very much. Even at full actuall carburetor plate full throttle it just wont rev very much. Adjusting the screw which I think is high idle or high speed does absolutely nothing. Using the choke just pisses it off and I wont get any fire at all. Valves don't seem to be sticking.
This engine is on the bolens I bought for 20 bucks...in another thread.
also have noted backfiring out exhaust. Some scoring on cylinder wall.... I have seen worse. My guesses are sticking rings, bad carburetor(although the high speed screw did work before), loose valve seats.
Used to be I could rev it, just was a witch to start or get continually running. Now I cant rev it much. Have taken apart carb many times now and blown it out.
Edited by quartermilecamel, September 02, 2013 - 07:59 PM.