2 Cycle Engine Problem

Old 12-08-02, 09:51 AM
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2-cycle engine backfires, stalls


Have a 15 year old Toro snowthrower with a 2-cycle engine (made by toro, not tecumseh, I believe) that has just started backfiring and stalling.

Obviously, fuel is not getting burned.

I'm looking for possible causes and potential fixes. Replaced the carb last year, but it ran fine afterward. This season, not so good.

It could be a carb adjustment or a broken choke dumping too much fuel into the engine.

Any thoughts before I rip into the thing?
Old 12-08-02, 07:08 PM
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i had a similar problem on a briggs, when i would use starting fluidit would start up but backfire and stall. the problem was that no gas was getting through the diaphram. this may not be your problemb but ti may help
Old 12-08-02, 09:47 PM
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Hello dano21!

Usually backfiring and stalling together is an indication of the engine not getting enough fuel. The cause of this is normally a restriction in the carb. Does it run better with the choke on, or partially on?
Old 12-09-02, 03:50 PM
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It does run marginally better with the choke on. . .I'll pull the carb and check for restrictions, maybe blow it out with some compressed air. . .
Old 12-10-02, 06:32 AM
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The problem that you are having is also an idication of of old fuel. Are you still using last years mix? Did you run the machine out of fuel before storing? Was there some left in the tank, and did you just add fresh mix on top of what was already there?

The older the mix being run through the carb, the greater the chances are that it wont burn, to the point where it wont run at all.

The easiest way to purge the fuel system of old fuel is to disconnect the fuel line from the carb, and prime the carb and discard the fuel that collects in the spit cup. (There are other ways to do it, but this is the simplest method to explain.)

Once you have totally fresh fuel in the system, and the machine is warmed up and you are still having a problem running off of choke, open up the adjusting screws a quarter of a turn each. If that cures the problem, you are on your way. If not, then it's on to other things.

If you are going to remove the carb and clean with compressed air, be careful blowing thru the fuel inlet. There is a fiber check valve in there, that can be damaged. That check valve assists during priming.

If you are up and running, tilt the machine back on its handle while running. You should encounter puffs of blue, nasty smelling smoke. That is old nasty mix that collects on the bottom of the crankcase. Each time that the engine runs through an intake stroke, a little of that garbage mixes with the fresh fuel, and decreases its effectiveness.

Hope this helps.
Old 12-10-02, 09:14 AM
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thanks for that advice. . .I'll give it a go this weekend.

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