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Is this the first start of the season? Was fuel left in it previously? What engine and model are we working on here?
Yes this is the first start of the season but we had the same problem last year.When I pull the rope to start it it fires and tries to run backwards jerking the starter rope out of my hand. It is so violent the recoil starter breaks. (and almost my arm also). Each spring I Drain fuel out of the tank and then start engine to run all fuel out of carburetor. Model #OH318SA Spec #221828B Engine Family 5TPXS3282AF
Thank you. The rope jerking is the clue I was looking for. This symptom is almost always a partially shared flywheel key throwing the engine out of time. You'll need to remove the engine shroud to gain access to the flywheel. If you don't have a strap wrench for holding the flywheel, take a length of clean cord like starter rope and place about 3' in the spark plug hole to function as a piston stop to keep the engine from turning. Leave enough hanging out for easy removal. Loosen and remove the flywheel nut and washer, then look at the slots in the crankshaft and the flywheel. They should be lined up exacty square with one another. If they are not, the soft flywheel key has sheared (it's supposed to under some circumstances to prevent damage to the engine) and will need to be replaced.
Keep me posted, and let me know if anything isn't clear....
What spec did you tighten the flywherel nut to when you replaced the flywheel? Was it set to 450 in. lb.? Anthing less and it may have sheared again. Is the coil set at 0.0125"? the valves at .004"?
But your symptom is almost always the key....