# Tecumseh 6.5 HP OHV starter pull back



## Spit2 (Jul 26, 2016)

I am helping a neighbor with her mower. It is a 15 year old Scotts (like the fertilizer) it was made by Murray for Scotts. It is a model 22965X8B. The engine is a Tecumseh Magna-Start Overhead Valve model OVRM120. When attempting to start the engine it will on occasion pull back the starter rope back so severely as to rip the handle right out of her hand. She does not have a lot of strength and she has a lot of trouble with it. I do not but I can feel it pull back on occasion. I know that the most likely cause is a sheared flywheel key or a loose blade. I changed the flywheel key and tightened the flywheel, as well as tightening the blade with an impact wrench, I have both of the cupped belleville washers that tighten down on the blade properly installed. I believe that the blade is not loose. Is there something that I am missing? Is there anything unique to a OHV engine with valve adjustment that could cause this. I am stumped. Any and all ideas welcome

Thanks

Spit


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## geogrubb (Jul 28, 2006)

On a Tecumseh you must remove the flywheel to check the key, it can be sheared but looking at it installed it will look ok.


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## finaprint (Jan 29, 2006)

With a starter rope likely it has a compression release mechanism of some sort for easier pull. That messed up could help it to kickback. Past that many older people have problems with rope starters, they simply do not have the strength and engine out of tune to not rip away hard from the starting rope speed instantly makes that worse. Maybe somebody can show her the procedure used to make bigger motors not kickback as much like on big single cylinder motorcycles. Basically you feel the rope out to determine when the motor is right close to compression before the hard pull, it lights easier like that. As well, the rope slipping out to a degree before it actually engages the crank to turn wastes pulling rope length and lends to kickback there too by shortening and weakening the overall pull effort. The pull then is more half-hearted and tends to kick more like that. The same as having an older person pulling on rope instead of a strapping young man. 

The timing may need to be artificially slightly retarded (normally not settable) to not make it kickback so much. If old enough to still be points then electronic ignition could help.

Live fresh fuel helps too, more aromatic and then engine lights off quicker and importantly, keeps on going more consistently.


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## Spit2 (Jul 26, 2016)

*Update*

Thanks for the replies, I have replaced the flywheel key even though the old one was not sheared. I just got the mower back tonight, tomorrow I want to look at the blade mounting and make sure I have it tight, I am planning on trying a different adaptor and blade if I have one that will fit. If that doesn't do it I am thinking that I should check the valves for proper adjustment. Does that make sense? I am assuming that an out of tolerance valve adjustment could cause the compression release to be out of time? I\Has anyone ever found this to be the case?


Thanks 

Spit


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## light mechanic (Jul 18, 2008)

you might try taking the spark plug out, turning the mower with the carburetor up and mark a place on the deck close to the blade, turn it a half round and see if the crankshaft is bent, start with a simple test then work up to the ones that will and may require an engine tear down, the old engines before the 80's had to be timed, that would pull back so hard it would almost pull you finger off you hand if not even the are at the shoulder, well maybe not that bad, Light Mechanic


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## finaprint (Jan 29, 2006)

It's kicking back from advanced timing. What sheared flywheel key does but other things can too. The timing is normally advanced and normal but if the engine does not pull up to speed instantly as in out of tune then it kicks back even with normal timing. Not getting a good long pull due to the pulley not engaging for part of the rope length does the same thing, the engine then is not fast enough pulling up because of less spin speed due to not a strong hand pull. 

Past a certain point old people will NOT be able to start without that problem, it is simply too much effort. Recognize that and give the woman a break. May be the only cure, waiting for a broken hand is too late. 

Crank not bent or the mower will be shaking your face off from the imbalance. If the blade is tight by simply trying to twist it on crank then not that. Make sure any centering washer on a universal type blade center hole is thinner than blade thickness or the blade can be loose. 

Setting valves likely will do nothing for kickback. 

The actual compression lowering method must be working correctly.

The old key does not have to be completely sheared, the timing changes even if the key has only yielded to be a 'stepped' looking key then, part of it has moved off from the rest. Same with the flywheel slot, which can be yielded as well. 

One can alter the timing to be at exact TDC or even a degree or two late and would help but affects mower power to a point. The motors are low rpm anyway and not nearly so wanting advance as higher load ones do.

Anything you can do to make ignition stronger helps, new plug, close setting of any mag unit to flywheel magnets (airgap) and the flywheel cleaned of any rust on the magnets. Same on coil.

Anything that would add flywheel weight can help too, say a heavier blade, the heavier weight then carries the crank more through the right way to not kick back the other way. Try starting a mower with no blade on it, it won't start and kicks back 100% trying to. It can even try to run backwards until the exhaust overwhelms the power stroke. BTDT.


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## nbpt100 (Jun 1, 2015)

With the valve cover off and the spark plug removed you can turn the engine around by hand and you should be able to watch the decompression feature working on the exhaust valve. When the piston is in compression stroke near the top you should see the exhaust valve open just a hair and then close. This would indicate it is working properly. It also sounds like a timing issue as others have well described it. If not, it is likely the decompression feature is not working at start up.

Does this machine have the option to add an electric starter? If so it may be a good idea for her.

Or just ditch the machine as the newer mowers are much easier to pull. 

I just had a 4 years old Lawn boy in with a Kohler 4 stroke engine. Very easy to pull. It is also available with an electric starter. If someone has a physical impairment why put them through the pain and uncertainty. The newer engines are much easier to start. They will enjoy mowing their lawns again. Good Luck.


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## finaprint (Jan 29, 2006)

Amen, the job is hard enough for old people as it is. I used to not bat an eye at lawnmowing but now I've come to dread it. My heart event changed all that, this Texas heat is killer even early in the mornings.


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