New Wheel Horse

[gsinal 1]

HI all. I am a new wheel horse owner. I got last year a 1989 520-hc it came with a 42 in rear discharge deck, snow plow, 36in tiller and a moldboard plow. It ran great for me last year. I started it up this year and it started fine but after cutting some grass for 1/2 hr it started to rev up and down. It smokes a little on start up. Also i ran it out of gas before this happened and wonder if i picked up something from the tank. it did not start right away but after i ran out of gas. It has a 20 hp onan with 1200 hrs which from what i am told is not alot for an onan engine. Any ideas as to what is causing the engine to rev. I would appriciate any ideas because i am new to onan engins and unfamiler whit onans.

[rmaynard 15,294]

:WRS: Glad to have you aboard. I will let one of our Onan gurus answer your questions since I am a Kohler man, but in the mean time, we would love to see some pictures of your horse. So when you get the chance, post a couple.

[Hodge71 664]

1200 hours is alot for an Onan. Most blow the exhaust valve on the rear cylinder around that tiime. My 416 has an Onan with over 1700 hours on it. All original, never opened up for any reason. It hunts occasionally like youre saying. SO theres hope that it isnt all of them. Some motors snuck thru that stayed together. I would venture to guess you got some gunk in the carb from putting her away last year with 87 octane fuel in her and possibly no stabilizer. She has crud leftover from the wonderful corn juice they shove in low octane gas nowadays. There should be a fuel filter that would catch any junk from the tank before it got to the carb. I use 93 octane because its been untampered with so far in the US. Alcohol is for drinking and for racing, not for our tractors. Onans arent really bad engines, theyre thirsty compared to a Kohler, theyre WAY expensive to fix, unlike Kohler, but as long as you keep the rear cylinder clear of debris the valve seat shouldnt shoot out of it. the carbs are finicky too from what I've been told, although mine hasnt had an issue....YET.....

[bowtiebutler956 649]

:WRS: You probably got some trash in the carburetor, I would take it apart and clean it first, and see if this cured your problem. It would be great to see some pics of your machine.

Matt :flags-texas:

[Challenger 27]

1200 hours isn't alot. I've had two 520h's, one had 1800 hours when I sold it and another over 1200 hours. Both still going strong. The Onan is considered by many to be a superior industrial engine.

As mentioned above, keep the rear cylinder clean.

[AMC RULES 37,102]

:WRS:

[Hydro 131]

Sorry to some..but I have to agree with Hodge from personal experience. (my own engine!) You will see more 520's around without engines than any other Horse and it's because the rear cylinder gives up it's valve seat due to excessive heat. Anyway that's another issue.

Make sure your carb is clean and properly set. If it's lean because of dirt that will cause the engine to run hotter and that's a bad thing for the rear cylinder.

I have never seen or heard of an Onan with more than 2000 hours on this site and I am sure that will invite some comments but not since last July when I first became a member have I heard of a running Onan with that many hours.... anyway....just sayin :hide:

[clyde 5]

i know a guy that has a jd with a 18hp onan with 2800 hrs smokes a little but waiting for the call that his deere has died :no:

[varosd 1,185]

Welcome aboard!!!I you might want to also clean the gas tank/replace gas lines/fuel filter also just dropped the gas tank on my 520 that I just picked up and you would not believe how much crud (grass clippings) I got out! My B-80 has the gas tank in front of the steering wheel and I think that keeps a lot of grass etc from getting the tank. V

[gsinal 1]

well i went out after dinner and messed with my tractor. Put some sea foam in the tank looked at the fuel filter and need a new on there is sediment in the there. Also while getting down to the carb there looks like a crank case breather that hooks to the air filter box and goes to the motor. the r of youubber hose part that hooks to the motor is not staying on is there a clamp for that end. got it to run smooth again i worked the choke back and forth and it settled right down. here is a picture. i will put some more pics up when i get the tiller on and running my mother need her garden tilled up and it sounds like a chance to use my tractor. I want to thank all of you for answering. I read alot of posts and really enjoy all the information.

[KC9KAS 4,741]

I was going to suggest a SEA-FOAM treatment, but I see you have already put it in the tank.

As stated earlier...the gasoline we have now (with ethanol) only has a shelf life of about 3 months. The fuel needs a stabilizer added to it when you store the tractor.

I actually use the stabilizer all the time by mixing it in a 5 gallon container then using the mixture in my internal combustion yard equipment (and motorcycles). The gas in the truck doesn't last a week, so I don't have to worry about the $4+ liquid gold going bad in there!

[WHEEL HORSE BILL 7]

:WRS: I have a 416 hydro that had the same problem up down same thing you got dirt in the carb for sure.A guy blew it out and cleaned it all out now runs like a champ good luck with yours.

WHEEL HORSE BILL :USA:

[gsinal 1]

Just because i hear some people do not like the onan engines, and they are confusing to me. i will run the one i got but if i were to repalce it when it goes because the tractor itself is like a tank is there a kohler or brigs that i coud replace it with. Its a p220. any ideas?

[Jake Kuhn 1,554]

:WRS:

[boovuc 1,090]

Welcome to Redsquare!

You can always put a different motor in that tractor. You would need to change out the plate it rests on and make sure you have it lined up to the PTO location. You would however lose out on the gauges that the 500 series tractor utilize. There is a Briggs Vanguard engine that fits in there and the KT series Kohlers will fit although the Series I engine has it's own set of "issues".

You can get the single cylinder K series to work in them but for the Hydro and bulk of a 500 series tractor, I wouldn't but anything less than a 14HP in it.

Run your Onan and keep it clean and regularly maintained. Just use them! They won't help get the job done by siting there looking pretty! :)

[SAM58 30]

Hello an Welcome to Red Square!

I have had a 1992 with 1600 hours, restored and sold. it is still running with close to 1800 hours, starts & runs better that my 1996 520 with 360 hours.

I think i need to do the carb cleaning too.

Keep it clean & serviced and you will get many hours of service.

[Wheel-N-It 2,968]

Your 520 is now 23 years old. I would recommend you set aside some time to remove the fuel tank and wash it out. Use Simple Green and rinse with water. Let it dry completely before you reinstall it. Replace all the fuel lilnes and install a good inline fuel filter. Remove the top of the carb, and the float (don't drop the needle). Then carefully with carb cleaner and a copper brush and Q-tips, clean the inside of the carb and the float to make look as new as possible. Then after reassembly, use only 89 ( or higher ) octane gas with Stabil (87 octane is nasty). I also mix 3ozs of Marvel Mystery Oil to a 5gallon container of gas. I have done the MMO thing for over 20 years.

Your fuel problems will instantly be gone.

Van

[ben06351 19]

Sweet 520HC! The 1989 Commercial should have the forward swept axles, the motion control lever location is different from the 520H, it's a bit faster and heaver. You really should keep her clean, the rear cylinder problems are no joke so keeping the big Onan cool is a must. I recommend you modify your belt guard for better air flow across the rear cylinder. That and all the rest of the fuel system advice that you have already received.
Oh yea btw now be careful because these Horses are addictive everyone seems to end up with a herd sooner or latter.
BEN

[refracman 167]

Like the others have said keep the engine clean, also Onan recommends that a 600 hr maintaince is done, which includes removeing the carbon buildup on the heads and also adjusting the valves. The Onan, unlike most engines, the valves tighten up, not loosen up, which could be a contributing factor as to why these engines loose a valve seat.

It is strange that this is a more common problem with the P220 on WH's than other brands with the same engine.

[boovuc 1,090]

Refracman brings up a good point in regard to the P220 Onan. Again, it's a great industrial motor that was used in many different applications. I think we see the issue more in Toro/Wheelhorse's use of them "COULD" be attributed to the belt guard in combination with the oil filter placement. Any Onan unless factory equipped with an external oil filter has that spin-on filter inside the tin of the rear or #2 cylinder. Other manufacturers mounted their Onan straight on with the crank coming out the back to run a shaft where WH/Toro has their's mounted sideways to utilize their simple and effective PTO belt drive.

That belt guard obstructs some air moving through the rear cylinder fins. This and the oil filter obstruction and the extra heat from it contribute to more failures on our Wheelhorses than other industrial and commercial uses the engine was used on. I do notice a lot of failed Onans on the green machines too but the way they are mounted makes a difference.

Just my humble unsolicited opinion.

Not wanting to hijack Gsinal's original post subject, run that 520 like you would any tractor you had before. Just keep what we hashed around here in the back of your mind and keep it well maintained.

[Hydro 131]

There is one other point I would like to add to what boovuc said. When you are mowing with the Onan you wil find they move a lot of air. Grass clippings get picked up by the left front wheel and the force of air under the deck. Then they are sucked up against the flywheel screen. If there was a lot of dead grass from the previous cut this will happen more frequently. Keep an eye out for this as the clippings will block air flow. They can lay in there pretty tight if you're not paying attention.

If I had it to do over again I would install a cylinder head temp guage because I think some of these issues could be detected before it becomes too late. I also think, there are times when maybe that 5 ft deck might be just a tad too much load

I have to say there is no sound like an Onan at work when you are standing back listening from about 100 feet or so or just after start up at a cold idle :music-listening:

[truckin88 104]

Check the govenor spring if it is reving like that.