I have a 5 year old Toro Powerlite. Bought it last week used. The owner said that it wouldn't start. Turns out that the recoil cord was hanging out so much, they couldn't get a good pull to turn the engine over. Anyways, fixed the recoil and check the carburetor needle and seat. The carburetor seems clean and the engine starts on second pull.
I pulled the spark plug to check found that it was black and wet. I think the previous owner may have run this engine rich or because the spark plug was not tightened properly. So I took out the muffler to take a look at the cylinder walls and the top of the piston. Cylinder walls looks good, no scoring. However, the top of the piston is all black. Seems like there's a layer of carbon. What should it look like if everything is running properly? What do you guys think the root cause of the black spark plug and piston?
I ran the engine longer today and it seems to be running right, no smoking at all after a few seconds. Also tipped the engine backwards to try burn all unburned fuel out of the bottom of the crankcase. I didn't have any snow to test the performance of the snowblower, but the engine does seems to run strong and the RPM sounds even, no surging or smoking. Apart from the loud exhaust and vibration from this little engine, it sounds pretty healthy.
I think I'm going to keep this machine for a couple years, so I've been cleaning all the oil and crud on the snowblower. Should I pull the cylinder head off and clean the piston? I think I probably need a new head gasket if I'm going to open it up. Is there any benefit of cleaning the piston? Or any detrimental effects of not cleaning it? Also, there are 5 or 6 head bolts, what's the tightening torque? The engine is a Tecumseh TH98 (similar to HSK600)
This message was modified Feb 5, 2012 by aa335
