Wheel Horse S420 w/Onan

[RonnieB 2]

My neighbor is a retired engineer and works on mowers on the side now. He has a 1990 or 89 S420 48 inch with Onan engine. Has 341 hours. He got the mower because of the electrical issue and corrected that but hasn't been into the engine. It doesn't leak or burn oil and purrs like a kitten when running. The belts are 2 years old but the tires are all dry rotted. They hold air but still no good. It runs strong too. Almost too strong. In high throttle you can't turn sharp because it keeps pushing you forward a little bit. It cuts well and on a scale of 1-10 on appearance, I would give it a 7 because the seat has two tears. It was garaged because the paint is still bright. He wants 950 for it. I wont pay that. I was thinking 600. Does that sound fair? 

[gwest_ca-(File Mod) 11,047]

Welcome to the forum.

The white decal under the left side of the seat should have the model number and serial number if it is not faded out.

The black hood decal was first used in 1990.

2 pages of search results for 1990 model 41-20OE01

https://www.wheelhorseforum.com/search/?&q=41-20OE01&type=downloads_file&page=1&search_and_or=or&sortby=relevancy

 

Garry

[ebinmaine 67,623]

1 hour ago, RonnieB said:

thinking 600

The appropriate selling price is the one that makes both the buyer and seller happy. 

 

If that machine runs solid it's worth ALL of 950 and then some. 

 

 

[Handy Don 12,237]

54 minutes ago, ebinmaine said:

The appropriate selling price is the one that makes both the buyer and seller happy. 

 

If that machine runs solid it's worth ALL of 950 and then some. 

 

 

I concur as long as the deck is in great shape--no holes or serious rust (look underneath!) and the spindles are not wobbly.

I may be wrong, but the deck seems older that '90. Any deck experts care to wade in?

Edited April 23, 2021 by Handy Don

[JCM 9,177]

to   Great tractor, grab it before someone else gets wind of it.

[pfrederi 17,741]

Forward swept axle+++

[Handy Don 12,237]

5 minutes ago, JCM said:

Great tractor, grab it before someone else gets wind of it.

Guessing in SC @RonnieB won't be needin' a snow blower!

[JCM 9,177]

@Handy Don  I'm a sucker for Winter pictures.

[haydendavid380 759]

If your trying to search for info you might have more luck searching for "520h".

 

I don't think wheel horse ever made an S420

[Chaz54 57]

Look on the deck to see if the model number tag is readable. Like the tag under the seat, the mower will have a model number that will identify what year it is also.

[953 nut 55,321]

42 minutes ago, haydendavid380 said:

I don't think wheel horse ever made an S420

The 1987 model 420 is one of the most collectable newer models ever built.

 

 

[Handy Don 12,237]

Looking at the image, S420 is a typo. It's a 520 Hydro.

[lynnmor 7,308]

That is a 1992 or newer, see that little step in the center console cover?  The seat and armrests are spent due to weather exposure and there are no exact replacements.  The chrome hubcaps are not there and they bring good money.  What is it with all the steering wheel center caps getting lost?  Unless the photo is way off, the paint has faded to pink and the tractor spent too much time in the weather.  An Onan will have numerous fasteners corroded and difficult to remove if it sat in the weather too much.  That deck is older than the tractor.  If the hour meter is correct and the oil has been changed regularly (fat chance), and corrosion isn't a problem, then $900 may be OK.

[tom2p 2,394]

properly maintained / serviced Onan is one of the best garden tractor engines available - gobs of power / torque and reliable 

 

poorly maintained Onan - with little / no service or sat too long without running or sat outside - can be a nightmare and should be avoided ( unless you are a skilled small engine type and willing to wrench )

 

[EricF 589]

One of the best things you can do for an Onan engine is make sure that all the fins on the cylinder heads are clean and free of grass clippings/gunk/critter nests. There's a rubber gasket that fits snugly around the oil filter on the engine and pushes into the gap around it in the engine tin cover. It it's missing (and it probably is) get a replacement -- they're available -- and put it on along with a new filter and oil change. That little rubber doohickey is important to keep air flowing over the rear cylinder head to keep it cool.

 

Likewise, make sure the hydro pump (under the fenders) is clean and doesn't have the cooling fins on it gunked up with dirt and clippings and oil. It needs to stay cool, too. Make sure the plastic fan under the right-hand fender is there and in good shape. Replace it if the fan blades are missing or chewed-up.

 

When working, always run an Onan and hydro at full throttle! That keeps the engine and hydro pump fans running at full speed, and keeps the oil pressure up where it belongs -- both important for long life.

 

Some folks get nervous about the Onans, but a little common sense and attention to maintenance will keep them happy and running well for a long time. One thing for sure, they're made to work and work hard.

 

If you're having trouble with the hydro drive pushing hard against the steering at full throttle and high speed, the speed control lever linkage down by the transaxle is probably cruddy and binding up, making it hard to get a fine adjustment of the speed. The cam for the control action is right under the seat, exposed through a big hole in the fender pan. Clean it up, apply some dry lubricant, and adjust the friction by loosening/tightening the nut on top of the slot in the cam plate. When it's adjusted correctly, you can go from creeping to full speed with no rough spots or difficulty setting the speed right where you want it. A little dry lubricant on the mechanism can help. Don't use anything that leaves a residue which will attract dust and dirt. (For a tractor that's spent too much time outside, you can try rubbing the cam plate down with a drop of good 30-weight oil or similar, then burnish it with a cloth until it's completely dry again. That works the oil into the pores of the metal and gets rid of surface corrosion. Make sure it's completely dry again, and then follow up with dry lubricant, and it should be trouble-free.)

 

Other things to look for on the steering behavior is the condition of the tires -- old front tires, with kind of a "glazed" surface on the tread, will tend to skid over surfaces. Especially if they're over-pressure. They only need 20psi or so. New rubber may be a big help. The torque from the Onan and Uni-Drive rear end are forces to reckon with. Ease off the speed with the hydro control to reduce the effect (which is why the hydro control cam needs to be operating smoothly.)