B&S Kickback While Starting

dave1949 · Oct 13, 2009

I have a 2 yr old Sears rototiller with a B&S 850 model engine. It has developed a bad kickback while pulling the started rope. Snaps the pull handle out my hand and leaves fingers stinging.

The engine has had several very fast/hard stalls from hitting rocks while tilling.

Should I expect to find a partially sheared key on the flywheel causing the ignition timing to be off?

Thanks, Dave.

jinman · Oct 13, 2009

My thought would be absolutely yes. A partially or fully sheared pin is surely what you will find.

Many years ago I bought a cheap 5.5 horse Tecumseh engine for a small riding mower. When I went to start it for the first time, it jerked the pull rope out of my hand and proceeded to completely destroy the start ratchet. I was baffled and called up the shop where I bought the engine. They got a good laugh out of my calling because that engine was designed for a rotary mower where the blade is flywheel mass. I had a small pulley bolted to the crankshaft and that wasn't enough.

Of course, that's not your problem. If your engine just developed the kickback, it has to be the shearpin causing timing to be early.

dave1949 · Oct 13, 2009

jinman said:
My thought would be absolutely yes. A partially or fully sheared pin is surely what you will find.

Many years ago I bought a cheap 5.5 horse Tecumseh engine for a small riding mower. When I went to start it for the first time, it jerked the pull rope out of my hand and proceeded to completely destroy the start ratchet. I was baffled and called up the shop where I bought the engine. They got a good laugh out of my calling because that engine was designed for a rotary mower where the blade is flywheel mass. I had a small pulley bolted to the crankshaft and that wasn't enough. Of course, that's not your problem. If your engine just developed the kickback, it has to be the shearpin causing timing to be early.

Thanks Jinman,

It's been about 30 yrs since I did any serious small engine work, was afraid I might find a whole new world when I went looking

It never used to kickback, I think it began about the same time as my rock tilling episodes. It would be a crime against machinery to put a decent tiller on my garden

It's on my winter to do list. Cleaned up and tilled the garden yesterday, it snowed a bit this morning. Way too early for that.

Dave.

alchemysa · Oct 13, 2009

See the recent thread regarding the B&S engine in the Craftsman mower. Sounds like a similar problem. Valve adjustment might be the fix.
http://www.tractorbynet.com/forums/lawn-garden/154333-my-craftsman-21-horsepower-b.html

dave1949 · Oct 13, 2009

alchemysa said:
See the recent thread regarding the B&S engine in the Craftsman mower. Sounds like a similar problem. Valve adjustment might be the fix.
http://www.tractorbynet.com/forums/lawn-garden/154333-my-craftsman-21-horsepower-b.html

Yep, I was reading that thread too. I will check the valve adj. while I am at it. Thanks.

PILOON · Oct 13, 2009

Reminds me of the old 22HP Jonson and Evenrude outboards.
If the manual spark was not at the correct position and you pulled real snappy like with a good grip, you could end up in the drink! (or loose some fingers)