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Hank F.
Hank F., Technician
Category: Small Engine
Satisfied Customers: 15197
Experience:  Certified on Onan and Generac generators
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I gave an Onan 4k genrator and need to know how to set the

Customer Question

I gave an Onan 4k genrator and need to know how to set the gas / air adjustment. The unit is hard starting and requires constant adjusting to get it started. Also is there an aux gas tank available as I have a restriction at the tank, several away and have thought about piping it in to the motor home engind fuel line. I put in a clear fuel filter and fuel pump. The Gen will run about 1/2 hr and die after burning all the fuel out of the filter.
Submitted: 2 years ago.
Category: Small Engine
Expert:  Hank F. replied 2 years ago.

Hello, my name is ***** ***** I am going to assist you with this.

Initial settings for the carbare:

Idle mixture screw = 1 turn out

Main mixture screw - 1-1/4 turns out

Start the genset and let it warm up for a couple of minutes.

Connect an AC voltmeter, frequency meter, and load bank to the genset.

Apply 4000W to the genset, and adjust the governor speed nut to get 59+/- 2 Hz.

Turn the main mixture screw in until the frequency starts dropping, Turn it out until it starts dropping again. Find the midway point where you get the highest frequency reading. Turn the screw an additional 1/4 turn out.

Remove the load from the genset, and check the frequency. It should be 62 - 63 Hz. If it is not, adjsut the governor speed nut to obtain it.

Turn the idle mixture screw in until voltage and frequency drop, and engine starts running rough.

Turn the idle mixture screw out until you get the smoothest running without surging.

Apply a full load to the genset and shut it off a few times to ensure that the droop is not excessive, and there is no surging.