Hello, I have a 1995 Snow Blower with a 10 h.p. Tecumseh HMSK100 engine in it. I rarely use it, it's still like new, but I just lent it out to a relative and it's not running very smooth. Never did, from day one. It always starts, and runs ok at full throttle, but wants to stall when idled down (not blowing) and when you throttle it back up it sputters and backfires until it reaches full throttle.
Does anyone know the baseline carb settings, so I can try that for now. The engine manual just says to take it to a dealer. There's one screw on the bottom of the float bowl (air screw I assume?) and I think two others on the carb. Can anyone tell me how many turns to set them at?
Thanks.
I agree that is is more than likely the main jet, which is on the bottom of the carb, That's also where all the "gunk" goes especially after seasons of sitting. The fuel evaporates, but some contamination resides. Years worth will foul the jet. Since it has been rarely used there is the possibility that there is some blockage or gunk in the jet or the bottom of the carb. It's usually not hard to fix.
On my Tecumseh 14 HP and others that I have serviced you unscrew the hex nipple under the carb that the main jet needle screws into. This is the jet holder and also holds the carb bowl on.
Get a rag and a container as about a shot glass worth of gas will come out (no smoking please
) You need to take off the bowl and sometimes you can just wiggle it off, sometimes you need to tap the side with a rubber mallet. There is a rubber gasket that goes around the top perimeter of the bowl and sometimes it's bound up there. A few taps with a rubber mallet usually breaks it lose.
Note two things.
1. There is a small gasket at the interface of the needle holder and the float bowl. Don't lose it and make sure that the area is clean when you put it back together.
2. if there is an indentation in the base of the carb bowl. If there is that is the place where the float pivots. It would be important to re-align the bowl properly when putting it back together.
Once everything is apart make sure to wipe out the bottom of the bowl and unscrew the main jet from the holder. Clean everything.
Now the hard part. The pointy end of the main jet needle goes into the main jet, which is up in the carb. Since you are not pulling the carb apart you need to run a fine wire up through that passage to make sure that it is free and clear. Me, I use a welding tip cleaning set and it has many different size serrated wires in it and odds are the one of them is the right size. If you have some ultra small drills you can use one of those (it just needs to go through the main jet, don't drill it out). In a pinch I have used the wire that is inside of the twisty things that you close the non zip lock plastic bags with. It's a paper thing with a wire inside of it. Strip the paper off and keep the wire straight and run it up into the hole. If you have some brake clean spray it would be real good to put the tube up into this area and give it a good shot of cleaner. But watch your eyes! that stuff burns.
Once it's all clean just put it back together and screw the main jet needle in until it just firmly seats. Then note the position of the slot and unscrew it 1.5 turns. That is the "normal" setting. If it's not running right you can open it up to 2 turns (richer), or close it a little (no less than 1 turn out).
I've gotten a good deal on several pieces of equipment that ran like crap, and they all had gunky carbs.
The stalling at idle may just be that the idle speed is not adjusted right. There is a screw on the carb that sets the most closed position of the throttle. Screw it in a half turn at a time and see if that helps. All it will so is just raise the idle speed. The other small screw is the low speed mixture screw. It is usually adjusted 2.5 to 3.5 turns out. But if the idle speed is set too low you can jack low speed mixture around a lot all for nothing.
If this simple cleaning and adjustment does not help out, then the smaller passages in the card are foulded and it would take someone that really knows how to pull it apart, and pull out the plugs that seal the low speed passages, to give it a good cleaning. Sometimes soaking the whole thing in a dip container of carb cleaner will work, but sometimes it all needs to come apart. But 90% of the time it's the dirty main get.
Good luck
Stuart
