Between the lawnmower and weedeater, I’m about to go crazy trying to fix stuff. I was mowing the yard last Saturday. I hit a big clump of grass stalling out the engine. Since then, it hasn’t started. I put in another spark plug. I cleaned out the carburetor. After that, I tried cranking it without the air filter on and realized it was backfiring. Well okay, I figured that had to be a sheared flywheel key. I got my cousin over here today and we took off the flywheel. The key is fine. There aren’t any points under it either. There seems to be no ignition components other than the coil. I’m baffled. Neither of us have an idea what else could cause the timing to be off. I turn to you guys, as this isn’t a good time for me to spend money on another mower.
What kind of engine?
Disconnect the sparkplug and turn the mower over (Aircleaner side up). Rotate the blade while observing it in relation to the mower deck. A bent driveshaft could be your problem. If it is, might as well buy a new mower.
If it is a Tecumseh (or possibly others, but I have seen this with Tecumsehs a lot) and the stop was very abrubt, I would suspect that the key between the flywheel and the crankshaft sheared. This screws up the ignition timing, and they won’ t run. A small engine shop, or even a good hardware store will have the new key and the flywheel puller you need to fix it.
Maybe it’s fuel delivery? Does it start or run if you spray ether or carb cleaner into the carb? My mower crapped out, and I did everything you did. Finally cracked open the gas tank, and found out that the fuel line that sits in the tank with the filter on the end of it rotted off, and fuel wasn’t getting up in the line unless the tank was REALLY full.
I left this message sitting for a while on preview. Let’s see if I can get it right this time.
It’s worn off the face plate, but I finally found that it’s a Briggs and Stratton.
I’ll try this, but I don’t think that’s what it is. I just hit a clump of grass which surely isn’t enough to bend a crank.
There has to be something on this rig that controls when it sparks, a set of points or an ignition module or something. I’ve found nothing of the sort and the only wire coming out of the coil goes to the killswitch. Is it possible there’s an ignition module built into the coil? The only other thing I can come up with is the intake valve is open when it sparks, brought on by a stuck valve or valve timing that’s way off. I plan on pulling off the head cover and checking that out next time I work on it.
It’s not fuel delivery. It’s blowing fire out of the carburetor. That has to be a timing issue.
Well I took off the head and found this:
http://img32.imageshack.us/img32/9710/dscf0739.jpg
The intake valve seat came loose and blocked the valve from closing. It makes perfect sense. I tapped it back in (though I can’t say if it’ll come out again), put it mostly together, and fired it up. I just need to put the air filter, shrouding, and all that back on it and I should be back to having fun mowing…
And yes, this lawnmower has seen some wear. I bought it from the kid who used to mow lawns around here, including mine.
Use a little JB Weld (steel epoxy) on that valve seat.
This can also be caused by a bent blade, especially if you hit a rock. Which just happened to me this weekend. Mower wouldn’t start again, and the blade looked all out of true when I rotated it, but when I put a backup blade on, it was fine. Turned out to be a flywheel key. So don’t toss a mower just because the blade looks unbalanced - try a known good blade first.