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Garden Tractors and Mowers Vintage lawn and garden tractors, mowers, snow blowers, snowmobiles and other old machinery that is driven by small air cooled engines.

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Sears ST12 Tecumseh Starter Difficulty Mystery and Carburetor Blow Back

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Old 07-20-2019, 10:00:08 PM
Glenn Ayers Glenn Ayers is offline
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Default Re: Sears ST12 Tecumseh Starter Difficulty Mystery and Carburetor Blow Back

Have ya tried a bigger .. better battery ?

"I'll have the Red Pill, thank you."
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Old 07-20-2019, 11:20:02 PM
Mark Abner Mark Abner is offline
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Default Re: Sears ST12 Tecumseh Starter Difficulty Mystery and Carburetor Blow Back

Been reading along, I have restored many Tecumseh HH120 engines for suburban tractors so here is my opinion, go back to engine basics, starter stall on compression will not cause excessive fuel to blow out the carb or flood the cylinder just like faulty carb will not cause starter stall. Don't confuse ignition timing with valve timing. Ignition timing fires the plug at the proper time in relation to number of degrees of crankshaft rotation, valve timing operates intake and exhaust valves in relation to piston location. every HH120 I have done the flywheel was a bear to remove, since yours came off easy I bet someone has been in the engine. It sounds to me like your cam timing is off. Remove the side cover of the engine, you will see a punch dot on the crank gear and a punch dot on the cam gear, rotate the crank and make sure these two dots line up at some point. This way you will know for sure your cam is set correctly. Put the side cover back on, next release the valve springs and pull the intake and exhaust valves inspect the seats then lap the valves for a perfect seal. This way you know exactly that the valve timing is set correct and the valves are seating on fresh seats.
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