Galloping Onan-24

Chuck White · April 29, 2013, 10:00:32 AM

Just can't figure out what makes my Onan-24 gallop!

It seemed to run just fine through the course of the Winter while it was in the garage. I would just start the engine off & on through the Winter just to keep it lubed, etc.

Now I was out on my 1st sawjob on Saturday and it started this new trend.

Not on low idle, just at full throttle.

Now, it will gallop when the throttle goes up in RPM's, like just before entering a log when I engage the drive belt!

Once it has to work, it runs strong and smooth, then starts galloping when I exit the far end of the log or cant!

I know there are several adjustments on the governor linkage!

Any ideas on how to fix it? :-\

Ocklawahaboy · April 29, 2013, 10:40:08 AM

I'm not familiar with a "gallop" hopefully that's because my onan 20 has never done it. Can you describe it in terms of chunka chunka, clunk clunk or vroom vroom? My fix-all for any engine is plugs and wires, then some sea foam.

Chuck White · April 29, 2013, 11:27:19 AM

"Galloping" (like a horse does) is a term we use around here!

Basically it means the engine RPM will pulsate from high to a lower rpm repeatedly!

When the blade is cutting, where it's under a load, the engine runs fine!

Also runs great when the engine is at an idle!

hackberry jake · April 29, 2013, 12:35:24 PM

I bought a used 20 hp honda that came off a pressure washer and it did the same thing. Its probably from sediment in the carburator. Mine has slowly cleared up as I have been running fuel through it. I am not familiar with the onans but you may be able to take out three or four screws to get your float bowl off and clean it out real well with a toothbrush and gas. Then just put it back on and try it out.

POSTON WIDEHEAD · April 29, 2013, 03:58:07 PM

This is probably not it Chuck.....check the air filter along with everything else.

beenthere · April 29, 2013, 04:35:41 PM

Governor feedback out of sync. -- maybe

NCDiesel · April 29, 2013, 05:05:38 PM

Quote from: Chuck White on April 29, 2013, 10:00:32 AM
Just can't figure out what makes my Onan-24 gallop!

It seemed to run just fine through the course of the Winter while it was in the garage. I would just start the engine off & on through the Winter just to keep it lubed, etc.

Now I was out on my 1st sawjob on Saturday and it started this new trend.

...snip...

Any ideas on how to fix it? :-\

Finally - something I can actually help on.

Hunting is caused the vast majority of the time by a lean fuel condition. Coming off winter storage, then it is most likely water/deposition/sediment/ethanol corrosion etc in the carb . Mix some Seafoam(or your favorite fuel system cleaner) cleaner in your fuel and see how much it improves. In my experience, Seafoam is the best at this. Do this and then see how it improves the condition. Generally it improves to the point of tolerable. Then constantly adding Seafoam over the next 12-24 hours of engine time eliminates the problem and prevents tearing down the carb.

Otherwise a minor carb cleaning/rebuild will definitely fix it.

BTW: The behaviour you are describing is "hunting". Governors "hunt". Galloping is pretty descriptive too - I like it!

PS: Don't mess with the governor. 99.9% of the time the governor is not the culprit

beenthere · April 29, 2013, 05:11:50 PM

How much seafoam should one add? as per gallon measurement?

dgdrls · April 29, 2013, 06:07:28 PM

Normal gasoline grades (including 10% and 15% ethanol blends)

1 oz. Sea Foam Motor Treatment per gallon of gasoline

Can mix up to 2 oz. per gallon of gasoline if necessary. Mixing at less than two-thirds oz. per gallon will impair the effectiveness of Sea Foam.

Ref, http://www.seafoamsales.com/recommended-mix-amounts/

I have used it in the past on some 4-wheelers that sat, it certainly helped.

DGDrls

SAnVA · April 29, 2013, 07:09:03 PM

My 20hp. Onan did the same thing when I first started sawing this spring but has evened out and running pretty smooth now. I use a gas treatment called Star-tron enzyme fuel treatment. A good friend of mine is a small engine mechanic and he swears by it, he says if everyone used it that it would put him out of business! He says that if you use any gas with ethanol in it that you need to use this stuff!

Jeff · April 29, 2013, 07:30:39 PM

I have this problem almost every year. You have to tear the carburetor apart and give it a good cleaning even blow it out with air. If you search on in and carburetor with my username you should be able to find some topics on it because it's an old problem for me. And I reckon it will be a new problem this spring as soon as I get around to starting the mill. Mine is in on in 24p. Or p24 I don't remember.

woodmills1 · April 29, 2013, 07:33:50 PM

As I have said, take the top off the carb and soak up the remains with a paper towell, air is fine too if you have it. Did this every time my oanan searched for correct RPM, and never had to get a new gasket.

Make sure non of the small spring ends have broken also

Jeff · April 29, 2013, 07:47:11 PM

I'm still using the same gasket as well. You may not get everything with a towel. Even a can of air like you use on computers will help. I also flush the bowl while the plug is out.

hamish · April 29, 2013, 09:00:02 PM

As mentioned before its just dirt in the carb. What model on carb do you have on your 24hp? Bouncing off the governor is usually dirt on the low speed side of things.

chet · April 29, 2013, 09:46:49 PM

Just went though this with da Onan on my JD lawn tractor. In my case I traced it to a lack of fuel, original vacuum fuel pump wasn't up to da task any more. I installed a new electric fuel pump, problem solved. Now it truly runs like a Deere. 8) 8)

sawguy21 · April 29, 2013, 10:17:33 PM

Hold the throttle shaft with your finger, if it smooths out the governor is set incorrectly. If it stumbles and stalls (more likely) the fuel system is at fault.
From what you are telling us the idle circuit is partially plugged. It is still in play even when the throttle is wide open under no load, the high speed circuit comes in under load when the throttle opens to it's widest point. If Seafoam in the fuel does not clear it up, you will need to tear the carburetor down and thoroughly clean it. Carb and choke cleaner accompanied by compressed air works well but be careful you don't blow small parts all over the shop. An o/h kit is bloody expensive, Onan is VERY proud of their parts, but downtime is worse.

Chuck White · April 29, 2013, 10:47:11 PM

Thanks for all the input!

I'll get some stuff ready and see if I can get it running properly this weekend!

I still have about 1,200 bf to go, to finish up the sawjob I'm on now and Saturday afternoon, I'll bring the mill home and see what happens.

Thanks again!

hackberry jake · April 30, 2013, 01:51:21 AM

If yours is anything like mine, it will only act up when people are watching. Otherwise it runs smooth as silk.

m wood · April 30, 2013, 05:19:27 AM

thanks for the thread chuck. my honda is doing the same thing and this helps me too. unfortunately, the dodge in the garage takes priority right now...maybe by this weekend I will saw again

dgdrls · April 30, 2013, 05:28:26 AM

hey Chuck,

If you can get some SF throw it in the mill as your sawing-out
your project. Certainly won't hurt.

Be well

DGD

Chuck White · April 30, 2013, 09:08:48 AM

Wife has a bowling banquet in Potsdam today, so I'll ask her to pick up some Seafoam!

Never used it before, but now, most anything is worth a try!

Jeff · April 30, 2013, 09:11:34 AM

I tried the seafoam. Your problem is not going to be fixed with seafoam. You just need to get the top off the carb and get in there and clean it. It is pretty amazing what gets past the air filters.

Quote from: Jeff on June 27, 2005, 11:19:37 AM
Well, it certainly needed it. I got lots of crud out of the thing. Once cleaned up it didnt seem to start or run any differently them before however. I'll know more when I run it. I need to saw about 100 BF of cedar yet ASAP so that should tell me if its better.

The first picture does not have anything to do with cleaning the carb but is a pic of one of the plugs that have less then one hour on them. They both look like this.

Top of the Carb off

draining and catching some gas.

yeck!

Before mopping out, pretty cruddy.

After mopping out, very cruddy.

There was enough in there to remove it with tweezers.

All clean assembled, and ready to put the breather top on.

pineywoods · April 30, 2013, 09:30:36 AM

seafoam might help if the problem is gum and varnish, but it won't do a thing for a piece of sawdust in the idle jet. Apparently this problem started all at once, which again says chunk of sawdust got sucked up out of the bowl into the idle jet (the orfice is small, probably about .020) Bite the bullet and pull the top off the carb..If you are lucky, you can blast the jet clean with compressed air. I have seen them so plugged up a small drill bit was required..

Chuck White · April 30, 2013, 09:42:31 AM

Well, I think the top will come off of the carb once I get it home where I have all the tools and compressed air to complete the job!

Will be either Sunday or Monday!

Thanks for all the suggestions and Jeff, thanks for the pics.

hackberry jake · April 30, 2013, 10:56:06 AM

Quote from: pineywoods on April 30, 2013, 09:30:36 AM
seafoam might help if the problem is gum and varnish, but it won't do a thing for a piece of sawdust in the idle jet. Apparently this problem started all at once, which again says chunk of sawdust got sucked up out of the bowl into the idle jet (the orfice is small, probably about .020) Bite the bullet and pull the top off the carb..If you are lucky, you can blast the jet clean with compressed air. I have seen them so plugged up a small drill bit was required..

I have also used a drill bit on jets, but I was after more horsepower on a four wheeler. ;D