# Onan Performer 18 revs bouncing



## bigcountry1009 (Oct 18, 2010)

I have a Miller welding machine powered by an Onan Performer 18 2 cylinder. The mechanism that controls the throttle is bouncing the revs. It's down and up, very rythmically. I never stalls though. I've rebuilt the carb because at first it would not run unless the choke was on. However, when I weld with it, it runs smooth as glass. When I finish the weld, it's right back to bouncing. Any ideas?


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## Basementgeek (Feb 7, 2005)

Hi and welcome to TSF :wave:

Has it always varied in RPMs or only since you rebuilt the carb?

My old, like 20 years, Homlite gen does vary in RPM when not under load. It too smooths out when a load is applied.

BG


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## bigcountry1009 (Oct 18, 2010)

I'm not sure, I got it used. I traded an old truck for it. It wouldn't run at all with out the choke when I got it. I could see a slight varitation in RPM, but it almost stalls then comes back up to operating RPM constantly. But it hasn't stalled yet.


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## Basementgeek (Feb 7, 2005)

Assuming that you put governor linkage on correctly, it must be a carb problem still. Try adjusting it a little.

BG


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## bigcountry1009 (Oct 18, 2010)

Well, on the linkage, all I did was separate it from the throttle shaft on the carb. There was just a little hair pin type clip holding it on. I'll try some adjustment on it. I see an adjustment and lock nut on it and several different positions for the springs. I've also been told that there may be some trash still in the lower jet. I was told it sounded like it might be "governor hunting". But I'll try some adjustment before I tear the carb apart again.

Oh, I forgot to mention that all the carb adjustments have factory plugs in them, so there appear to be no adjustments for me to make other than the idle screw on the linkage.


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## Basementgeek (Feb 7, 2005)

May need to pick a rebuild kit for it ?

BG


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## bigcountry1009 (Oct 18, 2010)

I've rebuilt the carb already, when it wouldn't run unless the choke was closed fully. Took a good look to make sure I didn't lose anything. Even tore into it over a rubbermade box just in case I did drop a part. I all went back together well.


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## k2skier (Sep 30, 2008)

It's called a lean hunt, I have seen this on brand new equipment, may have to get a new carb if a kit and a good soaking in carb cleaner doesn't work. I would try to set the float just a touch on the rich side and raise the idle some to compensate for this. You can try to adjust the governor, but it sure sounds like a lean hunt, once the fuel goes lean and RPM's drop the governor tries to bring the RPM's back up, once more fuel becomes available the RPM's raise again. I think it's caused by a lean idle circuit and no transition circuit from idle to high speed on small engines.


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## Wrench97 (May 10, 2008)

The old Millers I've used always hunted when not under load, Onan's designs tend to be for systems always under load like the gen sets they run 1 RPM all day loaded or not, we used to just set the idle up til the hunting stopped.


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## bigcountry1009 (Oct 18, 2010)

Thanks guys, I'm gonna take the carb apart once more and blow it all out really good. then try some adjustment and if that doesn't work I'm gonna let it ride. Thanks for the advice.


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## k2skier (Sep 30, 2008)

bigcountry1009 said:


> Thanks guys, I'm gonna take the carb apart once more and blow it all out really good. then try some adjustment and if that doesn't work I'm gonna let it ride. Thanks for the advice.


Simply blowing it out will be pointless...a carb dip and removing the welch plugs first is the only hope you have to remedy this.


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## bigcountry1009 (Oct 18, 2010)

Are those the factory plugs where adjustment should be? And will they go back in there?


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## Basementgeek (Feb 7, 2005)

No, you will need new ones.

BG


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