Lawnmower question: Fire shooting out of carburetor
 

After "fixing" my lawnmower, a process that involved scraping 1/8" of carbon buildup off of the inside of the head, snapping off two head bolts, reusing a damaged head gasket, and rebuilding the carburetor (I actually did this properly,) I soaked most of the engine in carb cleaner, and sprayed a liberal dose inte the carb itself. Starting it without an air filter and using 6-month-old gas (to which I'm fairly sure I added stabilizer last fall,) I discovered that to my surprise, flames shot out of the carb itself rather than out of the weak spots in the damaged head gasket. This was accompanied by the distinct popping of a backfiring engine, and to my disappointment, the entire mower did not go up in flames as I had expected. My current plan is to wait until after sunset and try again, as I expect the flames to be much more dazzling when not overpowered by direct sunlight.

My question is, what is the easiest way to make it stop doing this, and if that fails, what is the easiest way to blow up the mower in such a way that my mother will not expect me to fix it and instead buy another one (since we don't have a garage or shed to keep them in, we tend to buy an average of one mower every 18 months.)

Sounds like a timing problem to me. Did you move the cam or crank gear? Line them back up correctly?

also did you re adjust the carb?[if needed] what size engine is it and who manufactured it briggs and stratton ,tecumseh,honda? just wanting some more info,to be able to help more.

All I did was pop the head off. I didn't fuck with timing, and the carb isn't adjustable. Its a 6hp B&S engine, and toward the end of fall it was being a pain in the ass and only starting with copius amounts of starter fluid. If I stopped it, it would die for ~10 minutes (vapor lock?)

There was a lot of surface rust on various parts, but I cleaned it up and everything moves realtively smoothly.

Why is it that I can fix cars, yet am stumped by a backfiring lawnmower?

to make it run i would try a new head gasket, and get the two broken bolts out.and replace them. this way we know we are getting the right air fuel ratio.after tightning the head back down.as for junking it out maybe bend the valves, thus when you try to start it it will not and the bent valves,hitting the side of the seat,should make some bad noises. just some ideas?

Stop using starter fluid in a mower. If it doesn't start with a tsp of fuel dropped into the carb, it needs repaired.

It sounds like you have a sheared or partially sheared flywheel key. Remove the recoil starter, then the flywheel. The key it what "clocks" or "times" the flywheel to the crankshaft.

A new mower should last 5+ years if properly taken care of.

thats,another possibility,if before it was parked, a root,or brick,or a sudden blow of sorts happened to the blade, to cause the key to shear or partially shear .good luck with it.

Valve could maybe not be sealing properly.....well the best way to blow it up would be to pull off the governer and run her at WOT till she throws the rod.

Now that I think about it, I scraped a good amount of dead head gasket off of the head and block, and with 2/3 of the gasket gone, it still makes a seal but has a high enough compression ratio that it's detonating.

That is some funny shit there. I laughed my ass off. Best of luck mano, wish I could help.

Geez, and I've had the same mower going on 15 years now...

Tell her the piston rings a broken and can't be fixed....bamm new mower:D

You could always just add some ethanol to the gasoline mixture to make it go boom...

But seriously, most of the rebuilding advice has been covered. Personally, I'd just junk the thing (might get $20 out of it, depending on how good the mower is) and get a new one. And keep the damn thing inside =p

Recently, my mower has gone through the unhappiness that is 4 years without maintence, and has been giving me sputtering and pinging hell. Such are the perils when you don't care enough to take care of something (I figure $150 every four years isn't bad...cheaper than a lawn service and better than me spending time to fix the thing). Usually, I just use 'em until they die totally, or esplode... :evilgrin:

All I can say is... lawn mower racing... or tractor pull!

Comically, after I got it working, tho coil died. Fuck this mower.
I have nowhere inside to keep it. If I put it in the garbage shed instead of the garbage, I'll spend ten hours a week picking up raccon-invaded garbage aroudn the neighborhood. I can't bring it into the house, as we don't have a garage and I'm not dragging a gas-powered machine into the kitchen, even if I could fit it through the doorway.
It's a push mower.

Oh man, please, I beg of you, take a vid before you fix that and start up a big internet hoax about lawn mower nos. That'd rule!

Sorry to be a killjoy, but I jut got a new one. I may, however, see about turning this one into some sort of idiotic go-kart-like vehicle. If I stop posting unexpectedly, search for my obituary under "Jackass imitators," even though I've wanted to do it for quite a while.