Onan 400/500 Series

[boovuc 1,090]

Lets see some ways you guys helped your Onan's rear valves stay intack! Can you show us some belt guard venting that you've done?

Thanks,

BooVuc

Mill Hall, PA

[farmer 1,075]

This is what I did to my 518, can't say if its heading off valve problems for sure but its gotta help. Lightweight mesh spot welded on the inside.

[boovuc 1,090]

Thanks, Farmer.

Anyone else vent their 400/500 Onans?

BooVuc

Mill Hall, PA

[sorekiwi 761]

Anyone else vent their 400/500 Onans?

I'd like to do mine!

But I want a couple of louvres. I guess I need to make a set of louvre stamping dies to do it. I had been hoping that I might find something suitable in an auto parts accesories store that might bolt on, but I havent had any luck so far.

[farmer 1,075]

Please don't shoot me for saying this, but,

If you chop the guard and then put bars/louvres in the hole, your defeating the objective. You need something as course as possible that fingers can't get through. I suppose a copy of the louvred hood that some models have would look most authentic ( be careful which way you direct the airflow though. :D

[sorekiwi 761]

I hear what you are saying Rex.

Ideally I think I'd do 3 or 4 large ones, probably trying to stay about the width of the ones in the top of the hood on the 520's. I think I'd end up with about the same area as what you have in yours.

Also the air that is trapped back there has some pressure to it (from the flywheel) so really I think you just need to make it easier for that air to "spill" out.

One thing that amazes me with the Onan powered tractors is how much grass clippings collect on the intake to the flywheel blower. My grass is growing incredibly fast and thick this year, and I have to reach forward and wipe the clippings off the screen every time I go down the "straightaway". A while back someone here posted a pic of a screen they built to try to avoid this a bit, but I cant find it right now.

[boovuc 1,090]

I agree with you Mike!

I am amazed at the amount of clipping on the screen while I'm mowing. If there is a breeze while I'm mowing, I idle the engine down and use my hand to remove the clippings a couple times. If I didn't, the whole screen is covered.

BooVuc

Mill Hall, PA

[cheesegrader 433]

Farmer, I love your rig!

Couldn't you do just as well with a cluster of 1/2" drill holes?

Easier and cheaper than installing mesh, and might be a little stronger than louvers.

[can whlvr 993]

must be that big fan sucking up all the air and clippings with it

[DrabHorse 2]

I just cut my belt guard a couple weeks ago. Looks similar to the pic farmer posted above. Alot of air moves out of there now. Hopefully it helps the engine now with 850 hrs on it. I hope to go over this engine this winter and decarbon the heads and adjust the valves (is there info here on how to adjust the valves?)

[sorekiwi 761]

(is there info here on how to adjust the valves?)

Here is Karls link to the Onan Manual:

http://home.comcast.net/~lyon.family1/Whee...Onan_Engine.pdf

[SAM58 30]

I have wondered it a vent would make a difference?

Guess it can't hurt.

Someone need to make a bolt on Crome luvres with a template to cut out the hole, I say it would sell. :woohoo:

[Hydro 131]

There is another possibility! I was raised in the North End of Central Ontario. Minus 40F in the winter. Is anybody familiar with Bombardier? Ski-Doo? Years ago the vertical fan cooled two cyclinder 2 cycle engines used to run hot on the cylinder furthest away from the cooling fan and burn pistons. The 399 Nordic was a prime example. Don't know if you Southern guys even know what I am talking about but the solution for this was a cooler spark plug in the cylinder furthest away from the cooling fan! Today at least here in Canada, we are faced with ethanol in our regular gas. High and dry ignition! High octane here, does not have ethanol so obviously lower ignition temperature!

If I buy another Onan and I might... I will switch to high octane gasoline and a spark plug with a cooler heat range for the rear cylinder.

What do you guys think?? Don't know if it will work but from what my experience has been with my 416 and what I have read on this forum which includes all of the symptoms leading the end result every other issue has been identified. Some Onans cook the rear cylinder and some do not. Don't know exactly why but possibly depends on what they are called upon to do, the load and ambient temperature when they are worked. I sincerely doubt an Onan that blows snow will suffer this problem. :woohoo:

[jusjeepn 59]

No disrespect, but I think you guys are barking up the wrong tree. I agree that allowing some of the heat to escape definately won't hurt. Your still not eliminating the source of the extra heat, key word EXTRA, that blows over the rear cylinder. If you have had the tin off one of these Onans, you know that there is a MAJOR obstruction of air flow over the rear cylinder... the oil filter. The same air that is supposed to keep the cylinders cool is blowing right onto the oil filter. Now if you don't think that oil filter gets hot, try touching it after running it for about 15 min.

With the oil filter blocking approximately 2/3 of the air flow that is needed to keep the cylinder cool, you are inevitably gonna have more heat in the rear cylinder than the front. Now add in the air that does reach the cylinder is already heated from blowing over the oil filter.... Well do I really need to explain further...

[Hydro 131]

Great point. Another issue identified. That was mentioned before in another thread I think I read somewhere in this forum before.

What can be done about the oil filter? How would you move it? Bottom line is... still not enough cooling for that back cylinder.

[can whlvr 993]

sounds like a poor design to me,i think ill keep away from those onans :woohoo:

[jusjeepn 59]

Onan made an adapter that bolts on in place of the oil filter adapter. It has a pressure valve whichwill not allow the engine to starve, and a place to thread in a supply and return line for a remote located oil filter adapter. I have one of these adapters, but as of yet, I have not installed it. I still need to order the oil filter adapter and hoses to relocate it. I plan on doing this very soon so I'll report back to you with my findings.

[shorts 182]

The mail order speed shops/auto parts have remote oil filter kits, adapter to fit your engine, hoses,fittings and remote filter base usually to fit a ford style spin on filter. The remote filter will move the filter but the obstructuon from the base/adapter will still be in the cooling air stream. Has anyone considered that the oil filter was put inside the shroud so that it could act as an oil cooler?and that the factory remote kit is for ease of service in some applications. If you choose to remote mount the oil filter I would recommend that you make a cover for the oil filter hole in the cooling tins to keep the air on the engine cooling fins.