6.5 MCCK Onan Generator

[electricaldoctor]

We have tried everything to get it to operate correctly. I had the carburetor cleaned professionally, new plugs, wires, points, choke spring, idle speed valve, float level adjusted, adjusted governor, checked fuel filter and fuel pump pressure, etc. We also had a compression check done on the engine to eliminate any potential valve issues and that is not the problem. It will start and idle perfectly, but when the revs are increased, it will backfire and spew raw gas up through the throat of the carburetor. The power needle valve is slightly bent for some reason and cannot be replaced as the part was discontinued in 1990. I am now looking for a donor carburetor for my 1988 vintage generator. The carburetor part number in my Parts Catalog is 146-0313.

~Ken

 

[vernh59]

Ken,
I feel your pain. Onan is a great generator when they are right but they are a real PITA when they have a problem. At first I would say you are getting a lean pop when the motor accelerates but not if it is spewing fuel. Maybe they didn't get something right in the rebuild?
When I search for Onan marine generators on ebay there is usually a place that comes up in Arizona, I believe, that has a ton of used generators including Onan. They may be able to help with the donor needle. I would be inclined to buy a spare carb if they had it.

 

[fc3]

Does it backfire once when the throttle is opened from idle or does it backfire frequently when running at normal speed? It's only problem if the first and an entirely different set of checks if the latter.

 

[electricaldoctor]

It does not backfire while idling. It starts to backfire and spew raw gas up through the throat of the carb when attempting to increase the rpm's. I may have found a new carb for $210.00 ... will know tomorrow. It ran perfectly for the past 4 years, but started to get ornery last fall.