Small Engines (Lawn Mowers, etc.): idle mixture screw

Question
QUESTION: Hi David, i have an older ariens snowblower, model 924026 serial #020931 with a tecumseh 8hp, HM80155128c SER-6302D with an adjustable carb.I use to adjust the idle mixture screw at 3/4 turn out but now i have to put it to at least 1 1/2 turns out and the idle speed was at 3/4 in and now at 1 1/8 turns in to make it idle properly. I have cleaned the carb and installed a new carb kit and new float bowl but it still doesn`t work with the same settings as before. What may cause this.

thanks

Bruce

ANSWER: Bruce,

There could be a couple of different issues, one could be fuel quality, but an unlikely culprit, i would be betting on the orifices starting to narrow due to use. (think of the arteries to your heart narrowing due to cholesterol lol) I know you said you cleaned the carb, but unless you cleaned with an ultrasonic cleaner its really difficult to get the circuits completely cleaned.  You have two circuits in that carb, a high speed and an idle

Another possibility could be the screw although it looks the same is a little different in diameter than the one you removed

What ever the problem is by turning it out you are allowing the proper amount of fuel to flow and meet with the air mixture for a proper running condition.

Hope this helps

---------- FOLLOW-UP ----------

QUESTION: perfect, i took it out today and here in Montreal we had 20 cm of snow and it seems to idle well with the new settings.

Since you know a lot about chinese engines you are the one i need to ask about a project i`m thinking of. I`m contemplating switching my 8hp tecumseh(has 1 inch shaft) with a rato engine they sell here in Canada at my local hardware store. They sell 6hp and 7 hp rato engines on sale for $125. Are these good engines and what adjustments will i have to make to my snowblower if i swap engines: belts,engine mounts,pulley, etc.

thanks again

Bruce

Answer
Bruce, its really difficult to tell you without seeing the engine, however i can tell you from working over there they dont offer many options with a 1 inch crankshaft.  If you are lucky enough to find one simply put the pulley on your new engine from your old engine..PROVIDING the distance from the crankshaft to the base of the blower is the same.  You will need to remove the air cleaner as well and make some sort of a heater box to keep the carb from icing up.  HTH