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Old 11-19-2014, 10:02 PM   #1
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Default Onan 2.8KW Fix/Adjust Rhythmic Surging....Youtube

I have an Onan 2.8 KW generator in a 1994 RoadTrek that hasn't been run much.
With a 1/4th tank, I added "Seafoam" added 5 gallons then ran it for about an hour.
It runs with this rhythmic surging... reduces a bit with a load (electric box heater 1.5KW)

To clearly show this, I made this short 37second Youtube video to save on "a thousand words" to show what is happening.


Notice when I push on the choke lever part way that the engine smooths out. Push too far and it floods the engine causing dark exhaust smoke, back off and it runs smooth. Let go and its back to rhythmic surging. BTW I am 200 feet above sea level and the temperature now is 38F.

How can I fix this?

Bob O
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Old 02-06-2015, 01:16 PM   #2
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Default Re: Onan 2.8KW Fix/Adjust Rhythmic Surging....Youtube

Moved from Tweaks Mods & Projects to General Forum.
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Old 02-06-2015, 05:33 PM   #3
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Default Re: Onan 2.8KW Fix/Adjust Rhythmic Surging....Youtube

I've seen the same thing on small motors (aka, engines). I'll just shoot from me hind laig: you use gasoline with that ethanol mess? Try using all non ethanol if ye can find it.

Ye carburetor might just need a good cleaning. I found a youtube with a 12 year old boy who taught me how to clean my lawn mower carburetor. He was better than all those pros! "You see this thing here? Well, you ...." Non of this "The nuclear thermothingamajig needs to be recalibrated" mess.
"I thought I was wrong one time, but I was mistaken."
He's pinned under an outcropping of rock. Lucky for him, the rock kept the dirt from burying him alive. Dirt, it's nothing but dirt I tell ye.
That old man, he don't think like no old man.
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Old 02-06-2015, 05:59 PM   #4
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Default Re: Onan 2.8KW Fix/Adjust Rhythmic Surging....Youtube

As was said, non ethanol fuel if possible.

Get the tank to having 2oz per gallon of Seafoam (cleaning concentration). Seafoam works much better sitting than flowing.

Run for 30 minutes under load.

Let it sit overnight.

Run for 30 minutes under load.

Let is sit overnight.

Repeat as long as it takes, within reason, or it stops getting better.

Last resort is to turn the altitude adjuster to adjust the mixture. You want to go to a lower altitude setting to get richer, higher altitude to get leaner. You may have to take the plastic limiting cap off to get enough adjustment.

I think you will find that ethanol fuel will start to gum up in under a month, pure gas will last about a year. Remember that just running it once a month with gas that has been in the tank for 3 months is not as much help as the gas is old, and if it has ethanol, not very good. We preserve the tank at 1oz per gallon of Seafoma whenever the van is going to sit more than a couple of weeks, because we have ethanol fuel and want to be able to exercise the generator.
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