What does this sound like?

[GWGAllisfan 159]

12 HP briggs. Ran perfect weekend of 9-24, until shut down at end of job. See link http://www.simpletractors.com/club2/topic.asp?TOPIC_ID=53977 Tried to start it two weeks ago and it would fire and run for a short time then quit. Very hard to re-fire. ran out of time and patience and went in. Today went out to get a little tractor time out before dark. At first it wouldn't start, then with little starting fluid in the cylinder, it fired with heavy black smoke, began to run, then after a few minutes quit. This happened over and over again. Sometimes I could get it to keep running by holding the throttle closed and it would run for a while at idle, but as soon as it tried to accelerate, it would quit. This happened no matter what adjustment I made to the needle valve. As i worked with it, it got where it would only start when it was nearly flooded, then would run for a while and then quit. It acts like it is out of fuel, but I checked that. A few time it backfired, and a few times it had a backfire in the carb. The exhaust always seems to be rich, with black smoke, but the carb is dry when it quits. I thought it might be too lean, so I tried spraying starter fluid in the carb while it was running, sometime it helped, sometimes it didn't. the backfires concern me. Could this indicate jumped time or sheared flywheel key? Could it be fuel delivery? maybe a bad float or needle valve? I have a new Briggs carb I thought about trying next time I get time, just to rule that out. Any ideas? i may have to take the 10HP out of the other tractor if I can't get this one to run. Total score here: 4 engines, one runs....

[RayS 79]

Its possiable that you sheared a key. Did you hit something hard enough to stop the engine the last time that it ran. I have a 16hp on the shelf that does the same thing the key in the flywheel is fine it just needs bored and rebuilt, has real low compression.

[DarrellL 0]

You may want to check the float. I had the same problem with my tiller.After a new sparkplug and gasket kit for carb,I put in a new float and it ran great. Couldn't feel much in float but itwas just enough to effect performance.

[GWGAllisfan 159]

If i have time i'll try the other carb I have and see what that does. It seems like fuel to me, since it will generally run at idle. Is there any way to check timing with it in the tractor? Just to clarify, when i was able to use it last month, it ran until I turned off the key, not until it quit on it's own

[Jovee 0]

It's unlikely that the flywheel key sheared but anything is possible. Usually the belt/pulley will absorb any unneccesary shock. In my experiences you either have something wrong in the carb. A piece of spooge keeping the needle from seating, a worn or disattached rubber tip on the needle, a defective float with a pinhole allowing just enough gas in to weigh it down or a sticking intake valve. Make sure the crankcase isnt full of gas. It's easier to swap the carb than rebuild it so give that a try and see what happens-

[Simplicity314 0]

If it's not a fuel problem (another carb will tell you, as stated above) it sounds like a bad valve. That often sounds like a fuel problem as the valves will expand and contract depending on how hot/cool they get, affecting their clearances. Also, do you get the black smoke all the time? May be as simple as no compression because of bad rings.

[dhardin 0]

I'm totally guessing, A very durty air filter (nearly plugged) will act like its running on choke, but still run. As you was using it last with a plugged air filter you have fowled the plug over a time. When it was hot and running you was ok, now its cooled off and not getting the right air mix to a fowled plug. I just worked on a customers push mower (5hp Briggs) that acted and did the same as yours. But it did not back fire, that may be your use of the started fluied. Always check the simple stuff first.

[GWGAllisfan 159]

I'll let y'all know after I try the olher carb. I can rule out the airfilter, since it did the same with it on or off. Maybe next weekend I can work on it more....this is one of those times when not having a shop hurts.... BTW it has good cranking compression and a really hot spark.

[MikeES 454]

Only running on idle and you can't get it to accelerate sounds like poor compression. Maybe it is time to check compression and probably pull the head.

[D-17_Dave 12]

Not getting a good fuel flow. Pull the needle out of the bowl at the bottom and if your not getting drowned w/ gsa there is a restricktion. Work back from there.