QuestionI got a lawn tractor from my neighbor with a 12 HP, OHV Tecumseh engine. It would not start. I changed the gap on the coil (solid state ignition) and got it to start. I put the mower deck on and the tractor has enough power to run up slight grades in 3rd gear. The engine dies when I try to engage the mower. I eliminated the brakes on the pulleys on the belt drive (used to stop the blades)but it still wants to stall the engine. If I engage the mower for a brief period and then release the blades are turning and they coast for 10 - 15 seconds before stopping, but if I leave it engaged, the engine will stall.
When I reset the gap on the coil (solid state ignition) I did not set it to any value, I just left a small gap. Could this cause the engine to lose power? What is the correct gap? What should the compression be on this engine?
Also, once I got it running, the governor is causing it to run wide open all the time and it still does not have enough power to run the mower.
What else could cause it to lose power?
AnswerAre the deck bearings in good shape? Is there grass or other objects preventing the blades from turning?
The coil gap should be .010 and the spark plug should be .025-.030. Most 4 cycle mower engines do not provide compression. The book tells you to quickly turn the flywheel backwards and if the flywheel snapps forward on the compression stroke then there is enough compression.
Have you performed a leak down test? This will check the piston, rings, vavles and head gasket or sealing. You may have a leaky head gasket or the valve gap may be wrong causing the power loss.
Let me know what you find.
Eric
