Tecumseh hard pull start

14 years ago

Noticed this response to an earlier post regarding a hard crank problem believed to be caused by a compression problem:

"Remove the spark plug wire, remove the valve cover, and rotate the flywheel in a clockwise rotation by turning the blade. There are 2 rotations of the engine when piston reaches the top of its travel. You can "feel" this by putting a small screwdriver or other probe in the plug hole. With each TDC position, the magnet on the flywheel will have just passed the 2-legs of the ignition coil and will be to your left at the 7 o'clock position of the flywheel rotation. If the flywheel magnet is located in the center of the coil legs when you find TDC of the piston travel....flywheel key IS SHEARED. In in the "PROPER" 7 o'clock position....then the kickback is cause by an improper valve adjustment OR the mechanical compression release is NOT WORKING. Valves at TDC compression stroke should be @ .004 each. MCR problems requires replacing the camshaft."

I have same prob and attempted this test. Found the piston head not moving in cylinder (physical inspection while turning flywheel showed no movement while observing through spark plug hole and also after inserting screwdriver and flwheel rotation). Yet I hear oil sloshing and, when spark plug in place, feel "pressure" type resistance. My Tec. is an LEV120 361560B engine on a 20017 Toro. Could the piston in fact be broken away from the cam shaft (accounting for no piston head movement during rotation) and if so, can the sloshing of oil and cylinder pressure accompany this condition? Ultimately looking for a solution to a nonstarting mower.

More info: was left outside by my teenager and rained on for 2 days!@#%! Removed muffler and accumulation (water, gas, oil) came out.

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Comments (6)

ericwi
14 years ago
If the piston does not move when the flywheel is rotated, you have major damage, and the engine is very likely not worth repairing. It will likely be less expensive to replace the engine, or replace the entire mower, than it would be to attempt to fix this. It sounds like the blade struck something solid, and the connecting rod broke, so the piston is no longer connected to the crankshaft. If you know a local small engine mechanic, you might be able to get this fixed for a reasonable amount.
linden1
Original Author
14 years ago
Not the best news. But just so I'm clear, should I be able to see movement through the spark plug hole for this model engine, i.e. the "plate" my screw driver touches is the piston head AND turning the flywheel should result in the piston head's movement? While this may seem obvious, I just want to make certain there isn't a part of this I didn't accurately describe.
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ericwi
14 years ago
Its hard to see a piston head, looking through the hole where the spark plug goes. If you stick your thumb over the spark plug hole, and have someone rotate the flywheel for you, you should feel some air pressure against your thumb. That would be a crude compression check. You could bend a piece of coat hanger wire to stick down into the cylinder, so it has to touch the piston head, and then repeat the test, turning the flywheel. The piston has to move, up and down, as the flywheel is turned.
wantboost
9 years ago
I have the same issue on a 8hp tecumseh. I believe it's a hm80 non over head. So I shouldn't be able to see anything moving through plug hole? To verify piston is moving I would need a coat hanger??
If piston wasn't moving how would motor run?
1saxman
9 years ago
It wouldn't.
fishmech
9 years ago
If you have someone pull start the engine while you hold a finger over the spark plug hole, the pressure should blow by your finger if everything is operating fine. Since it is hard to turn over, suspect major engine damage. Pull the head off the engine and have a look. Any scoring in the cylinder, scrap mower and buy a new one.