surging onan

[woodmills1]

my 93 hd 40 has an onan 24.  Yesterday it was running fine but this morning on first start up it would not idle smooth, just keeps surging.  The governer lever keeps moving back and forth and it revs and then almost dies and revs and almost dies.  Acts the same when I pull the blade lever, but it seems to smooth out when the blade enters the wood.  I checked for obvious gov sticking but seems fine all spring are intact and no changes were made.  Any ideas, the thing has 2100 hours I changed the fuel filter and will try plugs tomorrow.  Could either the condenser or the valves be the cause, or am I way off.

[music_boy]

You should have a high speed air mix screw on the carb somewhere. Perhaps a low speed as well. I have twin cylinder B&S lawn tractor that does this all the time. Can't tell you why as I keep the fuel clean etc. But adjusting that high speed air mix does the trick for me. Like you I thought it was the govenor cause it acts like that . Doubtful in my opinion. Might just have a small piece of trash, sedimet on the needle seat, or lord knows what. Check your engine manual for the location, let her warm up, rev it and adjust it till she smooths out. Little carb cleaner if that clears it up and be prepared to adjust it again as it cleans itself out.
HOpe I'm right
Rick

[EZ]

I agree with Music Boy. I had to do this with my mower, but it wouldnt last long before it would start acting up again. I finally bought a new spring and o-ring for the idol screw and its been 2 years now since then.
EZ

[D._Frederick]

Wood-,

Wear in the governor linkage will also cause surging or hunting. Since this problem came on all at once, I would look for a fuel problem. If the engine is not getting enough fuel, the governor will open wide to hold the rpm.

[twoodward15]

Funny, I have an onan gen set and had the same problem.  Do NOT mess with the governor, it'll only get worse.  Your carb is dirty!!  Now, I cleaned one myself and took one to the small engine place and they put it in their washer.  Yes, I have two gensets.  Both doing the same thing.  got em for free.  They were headed for the dumpster.  Anyway, you know, I cleaned the one 2 times before I got it perfect.  They boiled that one, I haned them a ten spot and it worked the first time.  Now, your thinking your gonna clean it yourself and save the ten bucks, right?   Well, that carb cleaner aint free, so you just spent 4 of the ten dollars.  What it took you an hour to get that thing apart, cleaned and put together?  Time is money, you didn't forget the main jet running up the center from the bottom did you??  You know, the two piece jet???  Yeah, it's probably not budging either.  FWIW, I won't clean it again, I'll take it to get cleaned.  It was easier and cheaper to do it that way.  Save yourself the grief, although it was fun and I like doing that stuff, time is money and ten bucks aint much these days.  HTH

[Kevin_H.]

Woodmills,
I am have the same problem with my 97 onan, We have traced it down to the spring on the gov.

On our's the gov linkage that is running from the front of the motor to the back on the right side has a spring that runs over it. in other words the linkage runs though the middle of the spring, It is my understandin that the spring takes the play out of the linkage.

Just a thought.

[twoodward15]

that isn't true, the spring is just a vibration dampener.  Try tightening the spring or replacing it, it won't help.  Clean the carb and you'll be good to go!  
  When you get it fixxed, let us know what was wrong!!!

[D._Frederick]

Kevin,

Springs between linkage is to take the play out of the linkage connectors, this makes the movement of the carburetor butterfly sensitive to the governor. It will stop the engine from "hunting".  If there is a problem with the engine not getting fuel when idling, the governor will open up to bring the rpm backup using the the run jets. I would go thru the carburetor as has been suggested.

[VA-Sawyer]

When mine runs rough I drain the water out of the bowl and it starts running right again. I can get water in the bowl and won't see any sign of water in the inline fuel filter.  Drain the bowl into a small container so you can check for water.
VA-Sawyer

[Kevin_H.]

Well we put the new spring on today and the our surging problems went away...

Hey woodmills1 did you figure out what was going on with your '93 yet?

[MM]

I've seen this many times. It's a problem with the carb. On some of them just a good cleaning and rebuild would fix the problem. But, on some others it didn't. Many times when I worked for Wm we would try the rebuild first. If that didn't work we would chuck the carb and put a new one on. A new one always fixed the problem. If money is tight I would try the cleaning and rebuilding first. If not check it and put a new carb on.

[woodmills1]

Flash, it was the carburetor.  Finnaly got some time to work on it wednesday between customer fix it jobs, cleaning out my sister in laws house, 2 days on the footings for the garage addition and a funeral.  Woodmizer wanted 80 bucks for a rebuild kit or 160 for a carb.  I called the local carb shop and yes they had done work on onan's, mostly gensets, and yes they had done work on nikky carbs.  They said the nikkys they did were from forklifts and run around 95 dollars.  I dropped it off thurs morning and it was done by 2.  Get this 40 bucks.  Put the carb on friday morning and the onan hasent run that smooth for months.  Thanks for the good help from you guys.  And if you are near me it is Hobbs carburetor in Pelham NH.