Carburetor Sprays Fuel after Shut Off

[Old312-8 11]

I recently was given an old 312-8 tractor that I was told needed some work. Upon starting the engine, it was immediately idling low, so I adjusted the idle ever so slightly to get it to idle reasonably. Now the problem that I am encountering is that I cannot use the choke on the carburetor, or the engine will backfire (gunshot loud) even if I let it idle for 5 minutes before shutting off. If it doesn’t backfire, a spray of fuel comes out of the carb so I can’t run an air filter until this resolves. This makes cold starts and running the engine for extended periods of time difficult and with the plan being to sell the tractor, I just wanted to know if anyone knew how to resolve this.

[953 nut 51,511]

Sounds like it is time to rebuild your carburetor.                    I suspect someone may have been running Ethanol Gas which is the death of small engine fuel system. I would suggest you replace the fuel hoses and add a fuel filter as well as running ethanol free gas.   https://www.pure-gas.org/

[oliver2-44 8,834]

Yep, start with a tank to carb fuel system cleaning. Make sure their are gaskets between the air filter and carb and block.  You can make them out of cereal box cardboard if needed.  Also check that the throttle shaft isn't worn where it moves around in its bore.  air can leak there too.  if throttle shaft is loose, you can get a bronze washer out of those gray Hillman parts drawers at your local hardware store that will lightly tap into the recess around the shaft at the top outside .  When you disassemble the carb the screws for the chocke and throttle butterflys have been stake don the backside to lock them in place.  You need to use a file or dremel to grind off the back of those screws so the come out easy.  They break off very easily. ....Ask me how I know!

[gwest_ca-(File Mod) 10,478]

Just for fun see how it runs with the muffler removed.

 

Garry

[Jeff-C175 7,195]

Backfiring could possibly be a symptom of leaky exhaust valve.

[Tuneup 1,416]

Your problem, like all of ours for the most part, is that your tractor was someone else's and he may have been a knucklehead. Like we're saying, it's tuneup time - time to get to know that machine. I'd pull the head to decarbon and to check the valves. Check the lash, clean everything fuel related, check points and spark strength and make sure the PO didn't put some 10 psi fuel pump on the poor thing. Make sure that the plug is also correct. You'll be rewarded.