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Okay two days I have been fighting this Murray 3.5 Briggs Classic. This thing just will not crank it wont do anything at all! It sits atop a 20in push mower and I have tried 3 different coils and 2 flywheel brakes even different spark plugs. original spark plug was a RCJ6Y or to my knowledge new plug no change so I tried a RJ19Lm and nothing. When I got it the pull starter was broke so I replaced the top with another that's the exact same. The Model is a 9d302. Please help.

Will the engine turn over with spark plug out? If not the engine is probably seized up and not repairable.

It spins like a top. The piston moves up and down free and no sputter nothing with the plug out just spins faster. Could it be a compression problem?

ThatGuyYouKnow said:

It spins like a top. The piston moves up and down free and no sputter nothing with the plug out just spins faster. Could it be a compression problem?

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Do the valves open and close?

From what I can tell but not sure I haven't removed the head yet. I guess I should may do it tomorrow thanks for your replies ill look and see the ill post back

Okay removed the head and found the combustion chamber caked with carbon and the lower bolts were barely tight. The valves operate fine so I believe the head gasket is my culprit.

ThatGuyYouKnow said:

Okay removed the head and found the combustion chamber caked with carbon and the lower bolts were barely tight. The valves operate fine so I believe the head gasket is my culprit.

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Make sure to clean all the carbon off the head and top of the piston. Also I would put new spark plug in it.

Thanks for your help dumby me I should have checked that but oh well. thanks again.