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520H Carb problems

8 posts in this topic

ID: 1   Posted

I just came into possession of a 520H and have 2 problems- When mowing, the throttle drifts down from high speed to medium. Can't seem to find any way to fix it and also at a lower speed the engine speed varies (Hunts) Is there a way to adjust the governor? Herb

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ID: 2   Posted

:ychain:

The throttle control "creep" can be remedied by squeezing or peening the rivet tighter at the lever pivot. I usually remove the control cable ass'y from the tractor, lay it down on my anvil or vise, and tap the rivet with a hammer until the control lever friction increases. The only other alternative would be to buy a new control cable.

As for the "hunting"..... there's no doubt in my mind that it's a dirty carburetor. (It's an Onan and they're known for it. :hide: )

Here's the instructions - in case you want to try the governor first:

onangov.jpg

Both of my P216 Onans do it (more often than not) but since they spend most of their time at wide open throttle I never did anything to correct it. :scratchead:

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ID: 3   Posted

Herbs GT:

Looks like TT has you coverd so I'll just say hello and :scratchead:

P.J.

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ID: 4   Posted

Thanks guys for the help. I did squeeze the throttle cable pivot and it did help some although it still isn't quite fixed. I'm going to pull it out and put it in the vise and see if that will do the trick. I adjusted the governor and that helped a little. Guess that I'll just live with the hunting. It is not bad when you run with a wide open throttle. Seems to be a Onan trait. Herb

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ID: 5   Posted

I have owned quite a few Onan powered tractors and the surge at idle speed is pretty common.

I have had some success with Sea Foam carburetor cleaner. I use double the amount that they recomend in a full tank of gas and use the tractor as I normally would. Try to run it at least 30 minutes, then shut it off and let it set a day or two, run it 30 minutes at varying throttle settings from idle to wide open, repeat the process until you've run the tank nearly empty, try to never run one completely dry, you'll pick up every piece of crap that's been in the bottom of the tank for 10 years.

It's fixed the idle surge problem about 60% of the time.

I've used it about twice a year on my 416-H as a preventative measure and it's always idled smooth as silk, never had any surging at all.

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ID: 6   Posted

I've had the same experience with the Onans too.

Pulling the top half of the carb off & cleaning it helps a bunch too.

My last 520 actually had pine needles in the fuel tank...lots? :scratchead:

I had to service the entire fuel system & you'd be surprised what can make it into the carb.

Eventually enough crud gets through & makes a mess out of the inner workings of the carb.

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ID: 7   Posted

Stephen is right. I forgot to mention that the 40% of the time that Sea Foam doesn't work, I pull the carburetor off and clean it.

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ID: 8   Posted

Thanks TT for the advise on fixing the throttle cable. Gave it a good squeeze with a large pair of vise grips and IT WORKED!! Now to get some seafoam and run it thru the carb. We're getting there. This is one terrific tractor. Sent out all the tin to get stripped and sand blasted. Got it back today and primed it. Hopefully I'll be able to shoot it tomorrow with IH Red. Thanks again. Herb

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