Engine kick backs - Cord Pulls Out Of Your Hand

smallenginenovice

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Hi!
I have a Briggs & Stratton 5HP that I recently bought second hand. The problem is that the cord is being pulled back really hard quite often when I try to start it. My father is quite good with engines and have disassemble it and we still don't know what the problem is.

The flywheel key is not broken and the 2 vents seems to be good so we are planning on grinding the vents and put everything back. We also thought if the ignition coil has moved so it ignite to early but that didn't seem to be the case.

Does any of you have any ideas of what the problem could be?

Thanks!
 

smallenginenovice

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Check the keyway on the flywheel. If it's slightly twisted it throws the timing sequence off. This is very common if you hit anything with the blade it can shear the keyway. Pull the spark plug and ground it. Pull the nut off the flywheel and screw it on a couple of threads, pry up on the flywheel and whack the nut with a rubber hammer. Remove the nut and
you can see if the flywheel is lined up with the crank, then remove the flywheel and inspect the keyway. It should not be distorted. When you install it realize the keyway only locates position of the flywheel and it's the taper of the crank that holds it tight under torque. If that's not it check the valve lash and make sure the intake cam lobe is at the bottom position before adjustment. Some engines the lobe will drop slightly after top dead center as a compression release and if you don't find the bottom, you won't get the lash tight enough to reduce the compression at start. The comments on carbon are correct as that will cause an increase in compression and break your arm. You'll have to pull the head if that's the case.....good luck.
 

Hammermechanicman

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You can check the key without removing the flywheel. You just need to access the top of the flywheel and look at it and the crank. Checking valve lash on the 5hp horizontal briggs requires removing the carb and gas tank which is a PITA. To access the valve spring chamber.
Or
The total lift on both the IN and EX cam lobes is .233". You can remove the head and measure total valve lift and the subtract that from .233" and you get the lash measurement.
 

MNtractorGuy

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Hi!
I have a Briggs & Stratton 5HP that I recently bought second hand. The problem is that the cord is being pulled back really hard quite often when I try to start it. My father is quite good with engines and have disassemble it and we still don't know what the problem is.

The flywheel key is not broken and the 2 vents seems to be good so we are planning on grinding the vents and put everything back. We also thought if the ignition coil has moved so it ignite to early but that didn't seem to be the case.

Does any of you have any ideas of what the problem could be?

Thanks!
Many years ago I had this with a mower. A friend said tighten the blade. I said it was and he said tighten it again. I did as advised and the the problem was fixed. I doubt that you have anything serious wrong and blades do come loose on occasion.
 

DPP

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Hi!
I have a Briggs & Stratton 5HP that I recently bought second hand. The problem is that the cord is being pulled back really hard quite often when I try to start it. My father is quite good with engines and have disassemble it and we still don't know what the problem is.

The flywheel key is not broken and the 2 vents seems to be good so we are planning on grinding the vents and put everything back. We also thought if the ignition coil has moved so it ignite to early but that didn't seem to be the case.

Does any of you have any ideas of what the problem could be?

Thanks!
I had this problem and found it to be the carburetor. I had it off three times I finally replaced it and the problem went away. If I would of replaced the beetle and seat I think that would of fixed it.
 
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Well I can not believe all the long possibilities. The most likely issue is someone hit something and partially or completely sheared the flywheel key causing advanced timing and kickback. Pull the top down and remove flywheel nut and inspect the key very closely. If any, and even minor offset appearance, replace the key and see what you have.
 

Hammermechanicman

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Lots of suggestions.
The engine is a 130202 horizontal engine. It has a pulsa jet carb so it doesn't have a float or needle and seat in the carb so it can't leak. It is not a push mower engine so it has a cast iron flywheel and it does not have a blade attached to the crankshaft. So the blade can't be loose.
 
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