I have a 1995 snowblower 8 horsepower. Was running great, it started to backfire run rough and quit. Waited a few minutes and restart okay so I thought it may have suck in some snow, so I turned the shoot so the snow wasn't blowing back into the motor. Ran okay finished what I was doing, I shut it off too move the cars around and haven't been able to restart it. So I've put in the garage and heated it up to thaw it out, I prime the bulb, it backfire alot, then run for a few seconds and quits. I put some gas line antifreeze in the tank (not too much). I have taken the cover off and things look okay. Taken the spark plug out and it was wet with gas ( from priming it half to death and trying to start) Dried and cleaned and tested for spark, lots of spark at the same time I put my compression tester on 150psi. So it ran great and all of a sudden its not. It backfires, it will run a few seconds and backfires and quits. What else can I do BIG STORM TOMORROW!!!???

Judging by the backfiring I would guess a sheered flywheel key, remove the engine shroud, unbolt the flywheel and see.

is this a overhead valve system ?

first check to see if the flywheel key sheared also check to see if there is a sticky valve somewhere cause a valve that is sticking will cause backfire issues so will timing on the flywheel etc.

did you put antifreeze in before it started to backfire ?

or after words ?

also make sure the fuel you are using is fresh fuel and not got any water in the fuel cause water down fuel is a prime suspect in spitting sputtering backfiring etc.

been working on these since 1987

Thanks for the replies. How would you check for a sticking valve? I put the gasline antifreeze in afterwards because I suspect moisture might be the problem. The gas is fresh. I didn't hit anything to cause a sudden shock . What would cause the flywheel to sheer?

Forgot to mention it is a Tecumseh and pretty sure its a snowking. I could see a valve when I had the spark plug out.

HOLD everything.
Smokestack said "so I turned the shoot so the snow wasn't blowing back into the motor."
The symptom described could just be water in the fuel. Drain the fuel bowl and try again.

I guessing your right. However I wished I read this earlier, Blower was in garage all night with heat on it, cranked a lot this morning with same symptoms. I looked at the bowl and was thinking of removing it but it looked different than the ones I have taken apart before. It has a "set screw" that looks like in a nut. I didn't want to disturb it yet. Too remove the bowl do you just put a wrench on the nut and turn it off? Anyway the place I bought it might give me some warrenty so I just put the cover back on and loaded it into the pick up and I take it back tomorrow morning. I was wondering to myself if it is possible it was flooding itself, is it possible? Hopefully my repair guy can look at it fast but I bet he'll be very busy, if so I bring back home and remove the bowl myself. I'll let you know when its running. Oh yeah it a HM80.

Lawnmowertech said it first, although the symptom described can be any number of things, I'd lean toward water.
Quote: "also make sure the fuel you are using is fresh fuel and not got any water in the fuel cause water down fuel is a prime suspect in spitting sputtering backfiring etc."
Unless the warranty is "unlimited," if the reason it isn't working right is water in the fuel or any other non-defective reason, they're going to charge you for repairing it.

Older units often had a bowl drain. A little spring-loaded thingy that you pushed upwards.
The nut you describe is the main jet. If it has a spring-loaded screw in the middle of it, then it's an adjustable main jet, else it's fixed.

If you tip the unit up on it's nose, you can safely remove the bowl and nothing will fall out IF you remove the bowl straight out. If you pick up on it as you remove it, you could pull the float out and cause the inlet needle to fall out.

Of course, if you tip it up it may leak fuel from the filler cap - be sure to be in a ventilated area, away from water heater, furnace or other sources of flame / spark!

If the tank is near full, shut the petcock off if it has one, else pinch the fuel line carefully with needle-nose vise-grips or the plastic lock-off pliers made for just such purpose.

To keep the fuel from leaking from the gas cap use plastic bag screwed under the cap.ET

Happy New Year Everybody!!! Well I got it back from the shop today, they rebuilt the carb and put in a new spark plug and now is okay. We believe it to be bad fuel. Like I said I bought it used from them this past September and it had half tank of fuel in it, then I topped it up with fuel I bought for my boat this summer, lesson learned! The last time I posted here I took it to him and he was too busy to take it in but we figured the fuel, so I came back home with it and drain all the fuel and took off the carb and took the bowl off and cleaned it and put in a new inlet seat and needle, and o rings, I took out the needels and cleaned them I did detect a very small amount of varnish on them, I stopped short of pulling the plug out because the carb looked to me as pretty clean, put it all back together and had the same symtoms. Took back to the shop frustrated. Well I should have pulled the plug and went the whole way. Till the next time! Happy New Year