What should an Onan sound like?

sorner · #1 04-25-2021, 07:49 AM

I fell into a John Deere 318 with a B43G that the PO said was non running. I didn’t ask too many questions because it was in good shape and clean and really cheap. So I bought it and brought it home. The battery was from 2011 and swollen. So I put a good battery in it, put some gas in it and turned the key. I saw fuel go through the filter and it fired right up. It sounds pretty good but it sounds like a Diesel engine almost. Is that how they sound? I’ve never heard one running and it sounds different from my Kohler M20 in my Cub Cadet. It’s not a knocking sound or anything like that. The oil is good and clean. It has 1900 hours on it. The tractor had a good clean deck and everything. I feel like a thief!

R Bedell · #2 04-25-2021, 08:17 AM

Well, the few experiences that I have had with Onan, they similar but different than the Kohler Twins. Maybe a good thorough Tune Up is in store.

sorner · #3 04-25-2021, 08:29 AM

It sounds strong, throttle up and down is responsive. It doesn’t smoke. Inside the air filter is clean and not oily. I’m going to look at the plugs and change the oil and stuff before I try to use it. I also have to change the rear tires, I have a good spare set but one of the rears has a plug in it that isn’t holding and they’re worn down. The hole looks pretty big and there may be two plugs in it and it leaks down a day after pumping it up. Oh, and it had JD wheel weights mounted on it also.

Esteban · #4 04-25-2021, 10:13 AM

Most of my experience with Onans have been in generators, but they do have a " different " sound than most gas engines. Here is a video of one running. Fast forward to 4 minutes ;

https://www.youtube.com/watch?v=Sq4WJE4x1SU

sorner · #5 04-26-2021, 07:35 AM

Sort of hard to compare a video to real life but mine sounds like that I think. Maybe I’ll record a video of it running and compare that way...

Leadslingingdaddy · #6 04-26-2021, 07:38 AM

They have a bit of a more throaty sound esp under load.... 1900hrs is pretty good as i have normally repowered the JD 318/420 with other Kohlers at the 1500 mark for the Onans… Check the compression on both banks to get an idea of the internals....

Also the split intake manifold has been known to be a PITA....

Esteban · #7 05-08-2021, 09:02 AM

One thing I did not ask is what oil are you using ? My Onans have called for 30wt, & that is what I have used. I also use a NAPA/Wix oil filter.

sorner · #8 08-26-2021, 09:20 AM

I haven't had much time to play around with this tractor but I did mow with it once. It wants to bog down under load, and it surges and dies at idle without the choke on. It almost sounds like a misfire. So, doing my research on this issue it looks like it's probably a carb issue or an air leak in the split intake seal. I haven't checked the compression yet, I tend to do things backwards.

Both sides definitely have compression, I replaced the plugs and turned it over with the plugs out and both sides blow air forcefully out the plug holes. I have a compression test kit somewhere, but just haven't taken the time to pull it out. I put my timing light on both sides and the flash is smooth with no misfiring down to idle when it dies, so I don't think it's a misfire. Last night I finally pulled it apart to look around at the intake. It didn't look terrible to the naked eye, I cleaned it up and looked it over good. So then I decided to get my super bright mini maglight and turned off all the lights and shined it up in both sides of the intake and voila... there was light peeking through the seam in several places. So, following the guides online I took it apart and cleaned it up good and resealed it and put it all back together. I'll give it a good 24 hours to cure and then fire it up and see what happens.

I think the split intake has to be one of the worst ideas ever conceived. I wonder what was their reasoning for this design?

ol'George · #9 08-26-2021, 11:42 AM

Quote:

Originally Posted by sorner

I haven't had much time to play around with this tractor but I did mow with it once. It wants to bog down under load, and it surges and dies at idle without the choke on. It almost sounds like a misfire. So, doing my research on this issue it looks like it's probably a carb issue or an air leak in the split intake seal. I haven't checked the compression yet, I tend to do things backwards.

Both sides definitely have compression, I replaced the plugs and turned it over with the plugs out and both sides blow air forcefully out the plug holes. I have a compression test kit somewhere, but just haven't taken the time to pull it out. I put my timing light on both sides and the flash is smooth with no misfiring down to idle when it dies, so I don't think it's a misfire. Last night I finally pulled it apart to look around at the intake. It didn't look terrible to the naked eye, I cleaned it up and looked it over good. So then I decided to get my super bright mini maglight and turned off all the lights and shined it up in both sides of the intake and voila... there was light peeking through the seam in several places. So, following the guides online I took it apart and cleaned it up good and resealed it and put it all back together. I'll give it a good 24 hours to cure and then fire it up and see what happens.

I think the split intake has to be one of the worst ideas ever conceived. I wonder what was their reasoning for this design?

split manifold is less expensive to manufacture.

sorner · #10 08-26-2021, 12:33 PM

Quote:

Originally Posted by ol'George

split manifold is less expensive to manufacture.

Figures...