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Kickback from Tecumseh Engine

Posted by cuejal (My Page) on
Sun, Aug 17, 08 at 13:30

Hi,

First of all, I'd like to say thanks to the members for all that I've learned by reading this forum. But I have a problem that I need help with.

I'm working on a friend's Scotts mower (Tecumseh engine OVRM120-22032D) which is kicking back while attempting to start it. I've replaced the flywheel key, which was slightly bent, but that didn't fix it, so perhaps the crankshaft is twisted. The blade adopter key shows no signs of damage and the blade is tight on the shaft. The mower did start up once and seemed to run okay for a short period until I deliberately killed it.

A couple of questions.

- Can anything else cause the kickback besides flywheel misregistration, a twisted crankshaft or a loose mower blade?

- Does anyone know how many degrees before TDC the spark plug should fire on this engine?

- Does anyone know where the flywheel magnet is positioned relative to the sensor coil assembly at the moment of ignition, ie, is it centrally aligned with the coil assembly?

- Are flywheel keys available that retard the spark by a certain number of degrees?

I would appreciate any help. Thanks.

Jim


Follow-Up Postings:

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RE: Kickback from Tecumseh Engine

Not sure about that specific engine, but "some" engines have an offset key.

Kickback pretty much has to be flywheel/ignition timing.
I've seen it on a severely worn engine, where the flywheel actually had noticeable side play.


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RE: Kickback from Tecumseh Engine

I've got a Tec engine here that had a nudged flywheel key, so i replaced it with a new key. Went to start it, and got the "sheared key kick-back message".
Turned it up on its side--and there i found that whatever they had hit with the blade, had sheared off the alignment pins, and turned the blade a 1/4 turn. I replaced the adapter and installed the blade. But, no start, and still conveys the sheared key message.
I'm stumped! I used the same type key as i took out of it-so--whut?


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RE: Kickback from Tecumseh Engine

Thanks Bill.

To Bill and Rusty:

This probably doesn't apply to your machine Rusty, but I found the problem with my friend's Tecumseh. In addition to having a partially bent/unseated flywheel key, which I had replaced prior to posting here, I checked the valve lash. It turned out to be about 4X what the manual called for, on both valves! Apparently the compression release mechanism wasn't able to do its thing, at least not to the full extent, because of the excessive play in the exhaust valve train (which the CPR acts on in this case).

After adjusting that to spec, and replacing the recoil starter, which finally broke for good during prior testing, it starts nice and easy now.

Jim


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RE: Kickback from Tecumseh Engine

There is Two major flywheel keye used in Tecumseh engines, a grey aluminum one and a gold aluminum one. each one times the flywheel magnets differently and if you use the wrong one it will kick like a mule.


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RE: Kickback from Tecumseh Engine

'Apparently the compression release mechanism wasn't able to do its thing, at least not to the full extent, because of the excessive play in the exhaust valve train (which the CPR acts on in this case).'

I was going to say the compression release was not working but I did not know why. This is probably it.


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