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.

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?

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

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.

'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.