Just picked up an old Ariens snow blower, 1973 I believe, with a Snow King on it that is backfiring through the carb. Starts up cold and runs fine until under load. I assumed it is the carb throttle shaft and dug up another used carb and installed it, same thing - runs fine until I hit the snow then backfires out the carb! Any similar experiences? I'm wondering if it's hanging the intake valve or did I put another junk carb on it? I'd like to get it running hoping it'd be a good mini engine! Thanks in advance guys! :thumbsup::biggrin:
I have a H40 fro a 71/72 Ariens snow blower and once warmed up it would run the same way but only spit and sputter and occasionally back fire. It was just a carb adjustment.(fuel flow needle valve on bottom of bowl ) If you get heavy back fire its sounds like it's not the carb but if it runs smooth after start up I would try to adjust the fuel flow while running and see if you can smooth it out. Occasionally mine will vibrate one way or the other and it will start to do that under load , slight adjustment and it's good.
Lawn Boy; I'll try all that and post results. I've run this motor before I got it and it ran/runs like new. The guy made one pass down his drive and turned around and it started backfiring and lost all power but doesn't quit. I thought water in the fuel first but none, wondered about sticking points but they weren't burnt so I filed them and regapped them. Magneto isn't loose so timing should not have been affected. Plug looks good but you know what happens when you assume! I'll change it. Swapped the carb for another used one and it runs exactly the same - warms up smooth as can be, responds perfectly to both low and high speed adjustments (I know, should only adjust when warm but, I'd just put the carb on and didn't want it running lean) then starts belching fire and back firing through the carb so I assumed both carbs are good. Makes me wonder about the valves. Someone at my work mentioned the governor could be worn out but it is functioning fine.
Joker; Good compression and no smoke. I'll throw my compression tester on though when I pull the plug cuz it only takes a second and I won't rule anything out when I obviously don't know either!
WrenchDad & Phil I think I responded to you in there as well, Thank You!
Heater is on and I'm headed out. Thanks again all! :thumbsup::biggrin:
Joker; Good compression and no smoke. I'll throw my compression tester on though when I pull the plug cuz it only takes a second and I won't rule anything out when I obviously don't know either!
WrenchDad & Phil I think I responded to you in there as well, Thank You!
Heater is on and I'm headed out. Thanks again all! :thumbsup::biggrin:
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^^ I would check this. .004 is the diameter of a human hair. It may have sufficient lash to keep it quiet when cold but when it heats up and the components expand it's holding the intake valve off the seat .
Also sounds like the high speed jet could be lean, try opening the screw on the bottom of the float bowl 1 full turn (CCW)..if it doesn't help just turn it back. (It's unlikely it would run exactly the same with two different carbs...but you never know.)
Clogged inline fuel filter? Collapsed fuel line, crud in the tank filter screen, cracked fuel line or fitting drawing in air...all would make it run lean under a load or at high speed.
Also sounds like the high speed jet could be lean, try opening the screw on the bottom of the float bowl 1 full turn (CCW)..if it doesn't help just turn it back. (It's unlikely it would run exactly the same with two different carbs...but you never know.)
Clogged inline fuel filter? Collapsed fuel line, crud in the tank filter screen, cracked fuel line or fitting drawing in air...all would make it run lean under a load or at high speed.
CarPlay, Ran it with an inline spark checker and never seemed to have lost spark but that doesn't mean it isn't weakening spark. Found a pivot pin missing on the governor arm and replaced it and now I can get it to run better but like the carb is junk. Maybe go back to the original carb, check valve lash per roccosbike and KKK. Fuel tank and carb have been cleaned and new fuel line in place.
Again, thanks for all the input and help. Done for tonight but will report back with results of these suggestions.
Again, thanks for all the input and help. Done for tonight but will report back with results of these suggestions.