- posted 11 years ago
Got a B&S 12.5 HP engine on the lawn tractor. Model 28V707 if you
worry about such
Started to go a little strange recently.
It would blow off white exhaust, loose power and die. Oil fouled plug
and even oil in the carburator chamber.
Figured rings were the problem. But when I took it apart the rings
seemed fine. Thinking about it again maybe the oil ring gap was too
large and I intend to recheck it.
After I put it back together, I get what now seems like a timing
Turning the motor over gives me detonation once every so often but
the exhaust comes out the air filter!
OK. Timing problem. Right? But...
I've got the crankshaft lined up "properly" with the cam shaft. (Set
pips, drop the gear onto the crankshaft key.) There's only ONE way for
this to fit AFAIK.
Thought it might be the tappets. If the tappets were different lengths
affect the timing. So I reversed them. Nothing!
Checked other obvious things like valve return... Everything seems
My next idea is to visually check the piston cycles compared to
the valves and see if the timing looks about right.
I don't mind taking this sucker apart, but I'm runing our of ideas
about what might be wrong.
Tanks for any input.