Generator at High Altitude

When I re-jetted engines for 11,000 ft operation it did next to nothing. When .060" was shaved off of Onan flathead generators it restored significant power. A better-than-nothing comment.

Thanks to Tom. Yeah rich, less oxygen at alt.
Lean on oxygen. Rich on fuel.

Jets are cheap. Get one to have, but try the generator first before making the change. A little extra fuel smell in the exhaust may be the only difference.

Chances are that your generator will work fine @ +-5000' MSL without changing the jet. However, you may experience a few anomalies over time. Using the low altitude jet at higher elevations WILL cause the air/fuel mixture to be rich of stoichiometric. That will cause the exhaust to contain excessive unburned hydrocarbons and carbon monoxide and it may carbon up over time. The generator will use more fuel than necessary. You may also experience occasional spark plug fouling and the lubricating oil may become fuel saturated. If you change the jet, make sure you change it back if you descend in altitude and use the generator. If you don't and use the generator under higher/full load, the generator will now run lean causing excessive cylinder head/exhaust gas temperatures which may cause engine damage.

Chum lee

Somewhere in our Champion inverter genny manual it states that over 4K' a high elevation jet should be used, we live near 6K' and it ran just fine out of the box. Called Champion and they sent out a high elevation jet which I installed, could not tell the difference to tell the truth. You should be okay with the stock jet particularly if camping at elevation is not too frequent.

ppine wrote:
I live at 5,000 feet and the Generac works fine. At 10,000 feet it runs a little lean with the stock jets.

At higher altitude it would run rich. There is less oxygen to mix with the fuel.

Since the OP is only occasionally at high altitude, I would suggest not changing the jet.

Thanks for all the advice. Will give it a try, and see what happens.

I live at 5,000 feet and the Generac works fine. At 10,000 feet it runs a little lean with the stock jets.

I live at 6000 ft and I have a Champion 3500 I never changed the jet and mine will run my AC and I have never had an issue. I see no need to change it. JMHO

GWolfe wrote:
I had a Champion 3100 that I ran in CO at around 10,000'. It did just fine charging batteries, it even ran my friends Nuwave oven without issue. It ran on whatever jets were put in it from the factory.

Same here, do they jet them differently when being sold above 5,000 ft?