QuestionI just installed a new connecting rod and reassembled the engine. Now it backfires and does not run. The engine had 24.7 hours before this repair. I made sure the two timing marks were aligned on the crank gear and the cam gear. I adjusted the intake clearance, and left the exhaust alone as it was "in-spec". I lost the flywheel key and had to buy a new one, so the flywheel key is new. I set the Armature air gap to 0.010-inches which is between the high and low gap limits.
Where do I looke to correct this problem?
AnswerCheck the flywheel key first. Sometimes you have to lap the flywheel to ensure the fit is tight. Did you lap the flywheel to the crankshaft?
Did one of the push rods get bent? Make sure you check all 4 strokes, intake, compression, power and exhaust. Use a drinking or WD-40 straw inserted into the spark plug hole to see where the piston is with respect to the valve opening and closing...this will provide a good indicator of the mechanical timing.
At Top-Dead-Center and/or Bottom-Dead-Center, if the engine is timed correctly, there will be a very slight valve overlap. If you can verify the valve overlap you know for sure the engine is mechanically timed. Have you checked for valve overlap?
Let me know if the flywheel key is sheared.
Eric
