Onan SuperLoud 4000 - reduce exhaust smell

Thanks all for your replies.

I want to do easy/cheap replacements first. So I will replace the air filter and spark plugs. Do you think this is a good idea ?

No my Micro Noise 4000 doesn't emit visible smoke. Yours sounds rich due to stuck float or some other carb problem. It does have small engine exhaust odor similar to my Yamaha 3000.

Agree with Chris - have your generator serviced - tune up will likely resolve your issue or at least eliminate the obvious.

I would suspect air filter, 1st and easiest, then check choke setting, making sure it is wide open when warmed up. And do I remember the older Onans having an adjustable main jet ?
They are all noisy compared to Honda 1-2000, but not as noisy as my Generac/Kohler, but at least the exhaust burns clean.

WRT the noise, a lot of 'loud vs quiet' is in how good a job the RV makers do in installing it. If it's bolted directly to the frame in a bard metal compartment with a too-big ventilation opening in the door, and the outer end of the tailpipe tied down solidly so it can't shake? Yep, gonna be loud.

You need to get the Onan _installation_ manual for your model, and see what you can do to improve it. It details the required clearances and openings. Odds are that you can make improvements, maybe significant ones.

You probably should add the Onan resonator to the tailpipe; doesn't do much for quieting, but does smooth out the noise and lower the tone. Be sure the tailpipe is supported, but free to shake. Too-rigid mounting of that can prevent the built-in vibration isolation from working, since it's solidly tied to the engine.

But first you should probably also check the condition of the internal muffler at that many hours. Pull the generator so you can get the green top off of the box, and inspect the connection to the cylinder head and the rest of the muffler for cracks & other issues. Br sure the muffler-to-tailpipe joint is tight.

As far as odor, yes, check the air cleaner and the spark arrestor, and catch up any other maintenance issues. Also check the altitude adjustment. It is normal for the smell to be a bit worse at first, since it's running rich when cold, with the choke plate gradually opening as it warms up. You want to be sure that's actually operating properly.

Jim, "Mo' coffee!"

Has it had any maintenance whatsoever in its 1500 hours? Air filter, spark plug, run some seafoam through it- other things like oil change, clean the spark arrestor, de-carbon. The fact that it is loud is of some concern- these are relatively quiet, so there may be another issue.

Golden_HVAC wrote:

There might be a altitude setting on your generator. If you set it to 1,000 or less, it should make it richer, while a higher setting will tend to lean it out.

Good luck,

Fred.

There is also a Summer/Winter lever setting somewhere also. Your Genset may look different then this Photo.
Click this text for photo.

Home Skillet wrote:
Probably running rich.
Put a new carb on it.

Might be cheaper to check / clean the air filter first.

Golden,

The water cooled EV series has been discontinued some time ago. Had one in a '86 Class C and it was LOUD. High pitched whine from the cooling fans.

Jim

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