Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

I have an over 25 year old Ariens snow blower that I let a friend tune up :-(( Last night was the first storm I used it on and it started great but seemed weaker that it was when I started to throw snow. After it warmed up a little it started to backfire then got real bad as it warmed up more. I could see flames shooting out the exhaust. Any ideas what I need to adjust. I assume it is running to rich but I don't want to make it worse. Any thoughts.

Thanks Ivan

he has got the high speed jet too lean. the initial setting is 1 1/2 turns counterclockwise from fully but lightly all the way in. the idle mixture adjustment is 1 turn ourt from all the way in. if the engine starts and needs the choke for some time it's a clue it's too lean. if it backfires at full throttle when completely warm with no load on the engine reach under the carburetor and on the very bottom of the bowl vertically there is a nut and a screw.  this screw is the high speed jet.gradually turn the screw out or counterclockwise  and see if it smooths out and lessens the backfire. if it doesn't do any good reset it to where it was . if it was running ok before your friend worked on it the high speed jet adjustment should take care of it. other possabilities are incorrect float height adjustment, manifold air leak thru a bad gasket or loose manifold,blocket ports in the tube where the high speed jet goes into. warped or burnt valve.you will know when the carb is set right when it pulls hard under load without bogging down or black smoke,too rich! and doesn't backfire ,too lean. an additional test is to warm the engine thouroughly and go from high speed to idle speed for 10 seconds and throttle it back up to high speed. it should rev right up with no bogging or backfiring when correct. the idle mixture and idle speed are above the high speed jet but in line with the drive wheels. the top hole in the cover is the idle speed adjustment and the bottom hole is the idle mixture screw. if all else fails adjust the high and mixture screws as stated above. it should then start at this setting and try to smooth the engine out by little adjustments at a time. bagger!