Originally Posted by heretolearn
I was riding my Schwinn clairmont 7 speed cruiser with 80 cc engine today when the engine seized as I was riding. I was hitting about 29 mph when I heard a snap crackle pop noise that followed by the engine bogging down real fast. I also noticed after I heard the noise I heard what sounded like something metal bouncing around the engine. I was able to pedal the bike home about a mile where I took off the clutch cover to see if anything was wrong. Everything looked normal and the clutch was working as usual only now when you engage the clutch the engine will no longer crank over. It does freewheel but not crank over with the clutch engaged, Locked is what it is. I took off the spark plug to look inside and the piston is at the bottom position with no hope of turning. I am looking for any input on this situation,
Sounds like the top end seized up. A PITA but not really that big a deal. Most of the time you just buy a new cylinder, piston, rings, wrist pin and bearing (Don't forget the gaskets) and slap it back together. Sometimes you can save the piston if it's not scored up.
THEN---- You REALLY gotta figure out why it seized so it don't happen again. Was yer mix right? One guy thought he could put straight gas in it "just untill he got home" a few blocks away. (didn't work, seized it.) And sometimes carp happens for no good reason except it's cheap china carp.
Al Fisherman has a great thread on the whole process of rebuilding. If you can't find it get back to me and I'll do a search for it.