Onan

[dwcphoto 7]

Hi Folks,

I'm new here and have been very impressed with how fast you folks respond to questions and how much knowledge you all have. In the little bit of reading I've done, I seem to get the sense that Onans are not the favorite engines. I have a 518-H with an Onan. It's been running fine, so that's the good news.

In the event that I do end up with trouble, can a different make engine be put in as a replacement? What have you guys done in a case like this? Thank you, dwc

[farmer 1,075]

I had a 518, the onan was smooth and powerful, now and again it would 'hunt', but that was never a real problem.

Fuel economy was the issue for me...I traded for a diesel.

If you've owned the tractor from new, or a long time and serviced it / cleaned the cooling fins, it should continue to perform well for you. :thumbs:

[AMC RULES 36,945]

Yep, it's all about the maintenance. :thumbs:

[520HC 207]

Onan takes a lot of crap on this site.What is there several thousand members on here? Onan sold millions of engines,so all the bad mouthing is in fact a very small percent of the engines out there.I have seen Onan engines with 3000 hours on them and never so much as had the heads removed in that time. At one time Toro,John Deere,Ingersoll,Cub Cadet,Sears all used them,not to mention Onan Generators was top seller for many years,would still be if the EPA didn't force them out of the US.

I have seen many 520's with over 1500 hours on them.Have a JD right now with 1800 on it,and I mow 3 acres every week with it.

Just my rant for the day!!!

[can whlvr 991]

any onan i have personally known blew up at less than 1000 hours,but there is some good ideas about keeping the rear cylinder cooler,like moving the oil filter,putting holes in the belt gaurd and as stated allready making sure the fins are clean,im not bashing onans,wouldnt ever buy one myself but thats what makes the world go around,im familular with kohlers ,but as said onans are a good motor for some people,dont worry too much about the valve thing,many options are avaiable for transplants

[Jim_M 178]

I have never had an Onan go bad and I've owned several. I bought one last year that had a bad oil leak but still ran strong.

[546cowboy 301]

You know I have had three Onans with the rear intake seat out and have repaired them all. It's really not that big of a deal to do. But the ones I had I bought that way and I would just as soon not have the fact hat they can be repaired at a reasonable cost. Th darn things are pricey enough as it is. Just keep telling everyone to replace those Onans and I'll keep buying and fixing them. :D

[dwcphoto 7]

Thanks for the tips. My tractor lives in a shed out back and mice like to build nests in it. I need to make sure I keep the dust blown off of it. Does it hurt to spray it with a hose or do you guys use air? Thanks, dwc

[Jim_M 178]

As long as it's not hot, water shouldn't hurt a thing.

[boovuc 1,090]

I wouldn't spray it with water. The 500 series Wheelhorses used pretty thin wire connectors and smaller than it should have been gauge wires on their harnesses. Water and moisture are the enemy of the 400 & 500 series tractor's electrical systems. Keep them dry! I have a small 20 gallon compressor and I regularly blow out the fins after a few mowings on my 520 and 416 which are each powered by Onans. Truth be told, you should actually do this with any tractor no matter what it's powered by.

The P series Onan in the Wheelhorse 400 and 500 series have the oil filter sitting within the tin that directs the air from the flywheel over the rear cylinder head. This obstruction and the added heat of the hot oil within the filter has been pretty much documented into contributing to rear-cylinder valve seat failures on these engines. As everyone who has chimed in said, you need to perform maintenance regularly on these engines to keep grass, leaves, etc from getting into the fins of the motor. Regular oil changes, using synthetic oils and doing a few "mods" like cutting an "air opening" into the belt guard by the rear head and/or installing a remote oil filter on the engine can help keep the rear cylinder running cooler. Don't "over-work" the tractor! Keep the blades sharp! Make sure the spindles, pulleys, mule drive, etc are all lubed and are not tight. Don't cut super high grass in high gears! The list can go on but you get the point. The Onan is a smoother and more powerful engine than any "twin-cylinder" tractor engine I have ever owned and I have owned quite a few twin Kohlers and Briggs. They are expensive to fix due to their parts from Cummings. They do suck more fuel than similar HP Kohlers and Briggs. They are a bit more "complex" in their design and they can be a little tempermental but they are a good engine! Take care of it and it will take care of your lawn and garden!

Good Luck!

[JackC 616]

I like the sound of the twin cylinder Onans.

I have a 520HC and a 416H and they both start, run and sound great.

The heads and valves are supposed to be serviced every 200 hours.

There is a de-carbon kit available on ebay.

The fins on the back cylinder need to be kept clean.

I use Seafoam on a regular basis to try to keep the Ethanol from gumming up the carburetors.

I bought a second 416H with about 1,000 hours on the meter that broke a rod on the back cylinder.

When I took the heads off the carbon deposits were really really bad.

I bought a replacement rod and piston for a few bucks and will try to repair the engine when I find the time.

The valve seats looked OK other than a little wear.

Seeing that carbon mess after I took the heads off opened my eyes to the need for the 200 hour periodic service.

Compression tests are easy to do and should be done at least once a year to check the status of the engine.

[dennist 139]

I have an Inlaw that has the worst luck with his vehicles, he complains how they never last, they rot out, they handle poorly, and he never gets good fuel mileage.

-Ask when he last changed the oil-Never

-Ask if he has rotated his tires or checked air pressure-Never

-When did he last buy new tires-Never

-How is the air filter-Where is it located?

-Everytime he pulls in he has mud/dirt snow/salt all over it,Never clean.

-His vehicles are Expected to start and run second or third hand with no maintenance or care, and when they no longer run, all he does is bad-mouth them.

I can't help but wonder how many of these junk Onans were owned by my Inlaw?

[dwcphoto 7]

I'm getting the point here. I'll be replacing the rear with an 1100 and will have it stripped down pretty good to do that. It'll be a great opportunity to really clean it up.

What is involved in a head and valve service? I bet that hasn't ever been done. There are only about 400 hours on the tractor, but hard hours. It sat out before I got it and I regularly mow some high grass with it. I do change the oil and sharpen the blades and grease it.

I'll look up the de-carbon kit and see what that's all about, too. That Seafoam just gets sprayed into the carb?

Thanks! dwc

[1975wheelhorsec160 0]

the sea foam iv always had you pour it in the gas and it just runs throgh and cleans the carb

[dwcphoto 7]

Thanks, I'll look for it. I'm sure an auto parts store has it. Appreciated, dwc

[dwcphoto 7]

Can you tell me the name of the de-carbon kit? thanks, dwc

[jay in nc 209]

i put 7 hours on my 518 today had 3 different decks on it, it has 1548 hours on it now , the first thing i did this morning was to cut in a louvered pannel in the belt guard. you guys scared me on the hours & exhaust.valve seat problem. that said, you would be amaized at the amount of heat, dust & grass clippings came through the louver! Jay

[dwcphoto 7]

Hi Jay,

Can you post a photo of the improvement you did? I was thinking of something along those lines, too. Thanks, dwc

[Hydro 130]

One issue with Onan and Wheel Horse is nothing more than the placement of the engine with the rear cylinder air flow being blocked by the belt guard!

[varosd 1,185]

Jay, Photos of your mod would be great! there are previous threads of various belt guard mods such as using a bimetal hole saw and punching out a series of circles. And with those "Cool" NC Summers, the louvers will be a great modification. Did you do louvers like a hot rod hood? That would look neat to mimic the WH hood louvers.

I was under my 520 yesterday with a toothbrush, pointy piece of coathanger and decreaser cleaning out the rear cylinder fins of all the gunk! I even was fishing for clippings where the engine block meets the the mounting plate. vacum/blow/scrape..repeat. such a big engine stuffed into a "stock" frame. cleaning my "little" 8 hp Kohler is a breeze.

if you decide to replace the Onan, there are multiple RS threads on changing to Briggs Vanguard/Hondas/various diesels. backup WH's might be a option (and another excuse to the wife) !

[jay in nc 209]

don i took photos of the belt guard, but my computer won't import them right now, i said i put in a louvered pannel but what i put in has 56 1/2 in square holes 8 across 7 high starting right behind the pto where the guard is single thickness. it looks factory, 100% mig welded , & metal finished ,primed & painted. i have enough of this metal to do at least 30 belt guards. i have a 516, & 2 520 s that are curently not running & i am going to put the pannel in these guards,and if there is interest i will sell them on an exchange basic to help out members who dont have my fabrication skills. let me know if any one is interested, Jay

[can whlvr 991]

thats a

don i took photos of the belt guard, but my computer won't import them right now, i said i put in a louvered pannel but what i put in has 56 1/2 in square holes 8 across 7 high starting right behind the pto where the guard is single thickness. it looks factory, 100% mig welded , & metal finished ,primed & painted. i have enough of this metal to do at least 30 belt guards. i have a 516, & 2 520 s that are curently not running & i am going to put the pannel in these guards,and if there is interest i will sell them on an exchange basic to help out members who dont have my fabrication skills. let me know if any one is interested, Jay

thats a great idea :thumbs:

[dwcphoto 7]

That is a really good idea. What are you asking? Your new guard might be a little too nice for my tractor, unless you have some rusty ones... thanks, dwc

[jay in nc 209]

well how about $30 exchange + shipping $5.00 more for primed & painted. Jay

[dwcphoto 7]

That sounds very reasonable. Might as well paint it. Tell me what brand and specific color you'll use, as I'll have to do some painting on much of the rest. Where do I sent the $? Thanks, dwc