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Paul7


Joined: Mar 12, 2007
Points: 452

Why does an engine surge?
Original Message   Jan 2, 2012 6:40 pm
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.
This message was modified Jan 2, 2012 by Paul7
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jrtrebor


Location: Michigan - 3 hours north of Chicago on the lake
Joined: Feb 10, 2010
Points: 539

Re: Why does an engine surge?
Reply #4   Jan 2, 2012 8:41 pm
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?
niper99


Location: London Ont
Joined: Dec 2, 2007
Points: 354

Re: Why does an engine surge?
Reply #5   Jan 3, 2012 12:08 am
Paul7 wrote:
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.



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..

Paul7


Joined: Mar 12, 2007
Points: 452

Re: Why does an engine surge?
Reply #6   Jan 3, 2012 12:56 am
jrtrebor wrote:
Does partially choking it make any difference?

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.
This message was modified Jan 3, 2012 by Paul7
borat


Joined: Nov 10, 2007
Points: 2692

Re: Why does an engine surge?
Reply #7   Jan 3, 2012 8:59 am
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.
mkd55


Location: wisconsin
Joined: Dec 16, 2005
Points: 155

Re: Why does an engine surge?
Reply #8   Jan 5, 2012 10:23 am
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.
This message was modified Jan 5, 2012 by mkd55
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