I did something stupid on my Sears Ride On with Seafoam...

[buckeyefarmer]

Wow, i would never have known that would be the issue.

 

[JRobyn]

As previously noted, a backfire can cause a key to shear. They are evidently a very soft alloy.

 

[RandyT]

Zinc alloy

 

[buckeyefarmer]

In my experience with an old B&S engine, the key does not have to be completely sheared. Even a partial shear or wear is enough to change the timing leading to no or hard starting. I also would check the mounting of the coil too. A change there could have the same result as a sheared key.

Wonder if that would be my problem on an old push mower not running right, starts, but keeps reving and no power.

 

[Texasmark]

Don't blame the SF other than it may have loosened a particle of carbon which exited as a glowing ember and started the fire. SF is Naptha, Alcohol (the right kind), and mineral oil. Your gasoline is more volatile in terms of something to get a fire started. However SF is useful as a starting fluid for 2 stroke engines as the mineral oil does the lubrication that most starting fluids lack. I used it as a quick test for a 2 stroke that wouldn't start to answer the question: Spark or fuel?

 

[CincyFlyer]

Wonder if that would be my problem on an old push mower not running right, starts, but keeps reving and no power.

In my experience, a sheared key is the #1 culprit, if you have fuel and spark, but no start.

 

[Oldpath05]

If you are getting spark, and it won't pop on ether, check to make sure that the flywheel key didn't shear, thus throwing off ignition timing. I've had that happen with a violent backfire.

When I started reading this thread about the problem and the fixes, I wasn't sure what the problem was either until I read yours, as soon as I read it, I go yup bet thats the problem, then I get to the end and sure enough that was it>>>>good call :thumbsup:

 

[crazyal]

Wonder if that would be my problem on an old push mower not running right, starts, but keeps reving and no power.

My guess is ethanol has started breaking down rubber or the varnish that's built up in your carb. Either clean it or replace it would be the best place to start. With a sheared flywheel key the engine will not run.

As for the flywheel key, did you spray water in the carb when the engine was running? If so then it's very possible that you got some into the cylinder. The engine stopping quickly (because it can't compress water) can also cause the key to shear. It can cause much more serious problems like a bent connecting rod too. I would check (or change) the engine oil to make sure there's no water in it.

 

[Texasmark]

If you are getting spark, and it won't pop on ether, check to make sure that the flywheel key didn't shear, thus throwing off ignition timing. I've had that happen with a violent backfire.

Amazing how sensitive the timing is but I had a key only shear half way one time and engine wouldn't start....new key and that was that.

 

[4get gto]

My guess is ethanol has started breaking down rubber or the varnish that's built up in your carb. Either clean it or replace it would be the best place to start. With a sheared flywheel key the engine will not run.

As for the flywheel key, did you spray water in the carb when the engine was running? If so then it's very possible that you got some into the cylinder. The engine stopping quickly (because it can't compress water) can also cause the key to shear. It can cause much more serious problems like a bent connecting rod too. I would check (or change) the engine oil to make sure there's no water in it.

Funny that you talk about spraying water in the carb. I've done this many times to clean carbon off of valves & piston. Never any ill effects. Of course I'd spray just enough to keep it from stalling .