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Rick
Rick, Factory Authorized Trainer
Category: Small Engine
Satisfied Customers: 8030
Experience:  Outdoor Power Equipment technical trainer since 1990, covering eight states.
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My lawn mower kicks back when I try to start it. If I am

Resolved Question:

My lawn mower "kicks back" when I try to start it. If I am VERY careful and pull the
starter rope out just enough to allow for the first compession stroke the engine may
start. Otherwise, if I try starting it by pulling on the rope the "normal" way, the
mechanism either jams or, if the engine catches, the rope will be yanked out of my hand.
I suspect that the problem is in the starter assembly or a timing issue. Possibly a worn or sticking pawl or pully-spring assembly? Another thought is the the flywheel cup.
There is no specific info on the alignment of the cup relative to the flywheel, so I'm assuming the placement is not critical. By the way, the flywheel turns freely and never touches the magneto.

There is a second problem. Once I get the mower started, the governor control
assembly rocks back and forth causing the engine to rev up and down around one
cycle per second. Eventually the engine stalls.

Thanks, XXXXX XXXXX for any insight on this problem.
Submitted: 4 years ago.
Category: Small Engine
Expert:  Rick replied 4 years ago.
Have you checked for a sheared flywheel key?
Customer: replied 4 years ago.

Hi Rick,

 

Well, I was about to, but I could not find my wheel puller. However, I did do a visual

inspection from the top of the crank shaft and the slots in the shaft and the flywheel appeared to be in perfect alignment. The end of the key looks okay too.

 

One more piece of information. This is an old machine, as you can see. When my mowers get to a point where they are showiing their age, I assign them to mulching

leaves etc. in the woods behind my house. Occasionally I will hit a rock or a piece

of wood which may stop the machine. Once bent a shaft doing this, but generally

that does not happen. looking at the engine diagram, I'm also wondering if I may have

damaged the timing gear or the timing key. If all else fails, I'll do an autopsy on the

engine because I'm curious. Will share the results of the post-mortem with you if it comes to that. The only reason I'm trying to save this old machine is for its 6 HP

engine. One other thing I should have mentioned....... when starting the engine after

it has not been used for a while, it's quite "stiff" (ie the crankshaft does not turn as freely as it should). After running for several minutes the engine is quite loose....it's almost too

loose. Pointing to internal damage???

 

My wife say "junk it" but the engineer in me has to know what happend. Anyhow, I'm

electrical; not mechanical. Just took enough mechanical courses (theory) to be

dangerous.

 

Microphone to you Rick.

 

Rich

 

Expert:  Rick replied 4 years ago.

If the slots are lined up exactly then the key is probably okay. However, it doesn't take much. If there's even a ridge you can feel with your thumbnail that's enough to throw it off, and kickback is usually associated with a timing issue.

 

If there have been impacts, it's possible that the crank gear pressed onto the crankshaft may have spun slightly. An easy way to tell is to take the breather cover off the side of the engine and watch the action of the valves opening and closing. At top dead center on the compression stroke, both valves should be open, but at TDC on the exhaust stroke (180 deg. further on the cam shaft), both valves will open and close alternately as you come up to TDC and come back down.

 

It sounds like you may have some wear in the engine as well, based upon the stiffness and looseness you made comment to. when metal gets hot it expands and steel an aluminum expand at different rates.

Rick, Factory Authorized Trainer
Category: Small Engine
Satisfied Customers: 8030
Experience: Outdoor Power Equipment technical trainer since 1990, covering eight states.
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