# B&S lawnmower backfires etc



## goswwind (Dec 16, 2007)

hard starting, backfires, starter won't turn over on compression stroke. Back it off on compression stroke, hit it again, compression stroke won't turn it over starter gets hot, boosting does not help. Please help any advice. Once started it runs great. Please contact George at 
[email protected] :4-dontkno


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## Tumbleweed36 (May 14, 2005)

It sounds like your timing is off, due to you hitting something maybe while mowing. What happens with those as a rule is that when you hit something, there is a soft key that holds the magento/flywheel on and straight to the shaft. It is designed, so that the pin will sometimes bend (is soft, like lead) or allow the magneto/flywheel to turn slightly to keep the mower and sudden force from bending the crankshaft. If it bends the crankshift, the mower is worthless. However, if it simply has slipped or moved due to force, then you can just replace that key and it will work like new.

Don't misunderstand, some times the Crankshaft will bend and you have the same symptoms, but I would give that a try.

I would take the top off off the mower and examine that little key on the Magento/flywheel to see if it is bent or off center. If it is, simply replace it and see if that fixes the problem. I have had to do this numerous times through the years and it is an easy job. If the shaft itself is bent, then your mower is basically junk.

Someone who is a mechanic might be able to explain this better, but that is my opinion what might be going wrong and causing your problem.

Note: Most of the time you will need an inexpensive wheel puller to pull the Magneto/flywheel off of there without bending it. You can get those at most any wally world or auto store.


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## goswwind (Dec 16, 2007)

Thank you We will give it a try and see what happens.
George


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## Tumbleweed36 (May 14, 2005)

Give it a shot. Just start taking the cover off the top of the mower and work down until you see the engine where the Flywheel is on the shaft. If that little key or pin is bent or crooked or off center in any way, then change it. You have too look closely some times, and other times, it is about 1/4 inch off center if needing replaced. Good luck. Oh, you can usually see if it needs changed before you buy a wheel puller and there are some that will come off without a wheel puller, but most of the time, you will need the wheel puller.


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## les warren (Dec 27, 2007)

Also could be small particle of dirt under carb inlet needle, allowing petrol/gasoline to flow into engine. Does it spit fuel out of exhaust, is there a strong smell of fuel, check fuel hasn't flowed into oil sump. These symptons could cause hydraulic lock up stopping the engine turning on compression where as a partially sheared flywheel key would not prevent engine turning.


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