Please Need Help Bad Briggs Stratton won't Crank.

ThatGuyYouKnow

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  • / Please Need Help Bad Briggs Stratton won't Crank.
Hey guys new here but in desperate need of help I am a starting small engine repair man and have been fighting this lawn mower for two weeks now. It tries to crank but after a few rotations it kicks back like it hit something. I have changed the flywheel key three times, torqued it and readjusted the valves too many times to count. I have taken the carb apart cleaned and nothing. I have a BS 15.5 31A607 0458 E1. Please help somebody.
 

ILENGINE

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  • / Please Need Help Bad Briggs Stratton won't Crank.
Hey guys new here but in desperate need of help I am a starting small engine repair man and have been fighting this lawn mower for two weeks now. It tries to crank but after a few rotations it kicks back like it hit something. I have changed the flywheel key three times, torqued it and readjusted the valves too many times to count. I have taken the carb apart cleaned and nothing. I have a BS 15.5 31A607 0458 E1. Please help somebody.

Something to check, remove the valve cover, and remove the spark plug. Turn the engine over by hand and watch the valves. You should see one of the valves pop off its seat just before TDC. From your description I am betting on a compression release failure on the camshaft. The compression release return spring my be getting weak, and after the cam turns a few revolutions, it disengages the compression release and then you get kick back.

If you remove the engine to check the camshaft, just go ahead and replace it while you are inside the engine. Not worth the time to say, yep the compression release is still works on the camshaft, when you could still have a problem. I have seen them stick when the weight is rotated by hand, and sometimes it wouldn't stick, but replacing the camshaft fixed the problem.
 

ThatGuyYouKnow

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  • / Please Need Help Bad Briggs Stratton won't Crank.
Thanks that makes sense but didn't think it would happen to mine its only five years old. Is there anything else that could cause it because after setting the valves I turned it by hand but both valves function as they should could that problem still exist?
 

ILENGINE

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  • / Please Need Help Bad Briggs Stratton won't Crank.
My nephew MTD was doing the same thing last year. Adjusted the valves, and checked the valve operation for compression release. After a few starts. started kicking back again, so I replaced the cam and never had another problem.

My procedure is if I have to pull the engine to determine if there is a compression release problem with the camshaft, I replace the camshaft.
 

ThatGuyYouKnow

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  • / Please Need Help Bad Briggs Stratton won't Crank.
Thanks again I was thinking from under the valve cover but tomorrow will check to see. Edit: A better feeling of what is happening is it turns a few times while cranking then you see the flywheel bounce back then keep going. It seems as if the piston or something is in the way in the engine that's my thoughts. Could something might have broken off or come loose?
 
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