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

I started up my 11.5hp Tecumseh powered Ariens and it was surging.  Never did that before.  I'm not sure what causes an engine to surge/hunt but here what I did so far in an attempt to correct it.  I changed the spark plug, took off and cleaned the carb bowl and needle and float assembly.  Cleaned the jets with carb cleaner and ran a fine wire through every hole...even the tiny one.  It still surges.   Any ideas on what else I should try...or re-try.  

If it  helps the engine is the OHV variety.

40 years ago when I was in small engine class it was called the "Tecumseh gallop". It was so common back then they had a name for it. The carbs were junk back then. Some things never change. Thy soaking the carb and blowing it out after.

Have you checked the governor linkage? 

On my old L head Tecumseh engines, there was a screw on the bottom of the carb that I could use to settle the engine down.  Not sure what you have for adjustments on your carb.

There are also three tiny holes in the bore of the carb.  If your looking at it from the throttle plate end.  The holes are in the sidewall at about 3 o'clock.  They're tiny.  I believe they are part of the idle circuit.
Does partially choking it make any difference?

Paul7 wrote:

engines surge because there lean in the majority of cases... well if the carb is clean>>

1 drian the old fuel out and put new in

2 make sure the float is adjusted properely (with the bowl off and carb upside down i like to run the floats on tecumseh a little below paralle to the carb body...make sure its not flush with the carb body) or u run the risk of it running lean... and for good measure i would replace the needle and seat..it could also be sticking a bit.

3 make sure the intake bolts are all tight

4 make sure cylinder head bolts are tight

but before doing anything i would drain the old fuel and add new stuff..

jrtrebor wrote:

Thanks everyone for all the suggestions.  Yes it does help if I partially choke the engine.  Linkage all works freely.  Haven't made any adjustments...just cleaning. Also I didn't pull the entire carb...just the bowl, nut, needle and float. I changed the spark plug because the one that was in it was carboned up badly.  I'll try draining the fuel.  The gasoline was in from September with Stabil added to the fuel at the time of purchase.  The tank was run dry but in September I got around to replacing the belt and added gas to make sure everything was good with the new belt.  I did have a squirrel gnaw a small hole in the gas cap over last winter but I don't think that the "extra vent" would cause a problem.

You might want to explore the fuel cap vent a bit more.  Make sure that it's actually venting.  Fire up the engine and loosen the cap.  See what that does.  The squirrel may have left small particles of plastic that may be impeding the vent.

paul 7! everyone above has good advice,i would particularily pay attention to the orifices in the brass nut that holds the float bowl on.use a small wire to wiggle through the holes to make sure they are clean.if there is a high speed needle jet in the center of the brass nut you should be able to cure your surging by going a tad counterclockwise(richer).when it starts if you have to keep the choke on for a long to keep it running you are lean. check all gaskets from carb to intake, and intake to engine.carb clean with jets adjusted correctly,float height set,  no breathing leaks,and good fresh gas, engine should run without surging.i would also dump a good shot of carb cleaner in the fuel.