Need Advice on Maintenance...Onan 20HP on 1997 520-H

[ATolles 52]

Just bought a 1997 Wheel Horse 520-H. The meter reads a little under 300 hours. Do I need to do some serious maintenance? I’m a little hesitant to open the motor as I have never done that. Thanks.

[kwalshy 225]

No serious maintenance on the engine is required unless you're experiencing a specific issue, like smoke billowing out of the muffler.  I recommend the normal activities like, spark plug inspection, change the engine oil & filter, clean or replace the air filter.   Refer to Onan O&M manual.      

[chex313 123]

Keep the cylinders cleaned....and at some point you can check the compression. The valves do need  periodic adj. There are couple of threads that are recent,(because I just had to do it) on the subject. If you can use a feeler gauge it will cost you less than $75 including , compression gauge, and gaskets and feeler gauge.

If its running good you may have a couple 100 more hours (or more) till its becomes an issue.

 

You only need to pull some tin , exhaust and intake manifolds and that will give you excess to the covers for the springs and adj. 

 

 

 

It will look like this for adj

 

 

 

Edited June 3, 2020 by chex313
added info

[lynnmor 6,762]

Valve adjustment is at 1,000 hours.  I would service the air filter, change the oil and filter and replace the spark plugs.  Make sure that the grommet that seals around the oil filter is in place, they often are lost. 

 

While the oil filter is off, use a flashlight and mirror and look up at the fins, if you see much debris or oil residue, clean that out.  This is a miserable job but you need to keep that area clean to prevent a loose valve seat.  Usually they are clean, I have one with 1400 hours and it never accumulated enough to matter.  While mowing, the screen accumulates a lot of clippings, so brush it off in a way that doesn't send the clippings inside.

 

Change the transmission oil and filter now.

 

Grease the chassis often, particularly the pivot for the front axle and the fittings pointing straight front at the ends of the axle.  Jack up the front to do these three fittings so the grease flows where it is needed and flushes out the debris.  These axle points are plain bearings and you don't want wear there.  I hit them almost every time I mow.

 

Most everything you need to know is in the manuals available on this site.

[kwalshy 225]

https://www.wheelhorseforum.com/files/file/6-engine-onan-p216-p218-p220-p240-sm-492-4006pdf/

 

Link to Onan engine manual

[squonk 38,844]

Use a Napa 1410 filter and Mobil 1 10-30 for the hydro.

[tom2p 2,393]

 

gotta keep the blower housing screen clean 

can depend on the grass (height, moisture, etc) - but there will be times when the grass clippings or leaves will need to be removed frequently from the blower housing screen as you are cutting grass 

 

( there are times and areas when I will need to reach down and remove the clippings or leaves after almost every other pass )

 

the fan moves a significant amount of air - and will suck clippings from the lawn / front tire as you mow over an area a second time (if you cut an area a second time that was cut just earlier)  ... I see this when I cut tall grass - first cut with deck in upper most position and then a second cut with the deck lower  

 

and in the fall with heavy leaves - if you don't rake be prepared to clear a lot of leaves 

I will often run through a large area of heavy leaves in the fall and will need to frequently clear the screen 

 

another area to check is under the 'console' /  seat area - grass clippings can accumulate in this area and can almost blanket / insulate the top and one side of the Eaton trans 

 

( don't ask me how I know this  lol )

 

just need to remove some screws (4 ?) to remove the plate to access this area 

 

Edited June 3, 2020 by tom2p

[lynnmor 6,762]

2 hours ago, tom2p said:

 

another area to check is under the 'console' /  seat area - grass clippings can accumulate in this area and can almost blanket / insulate the top and one side of the Eaton trans 

 

just need to remove some screws (4 ?) to remove the plate to access this area 

 

 

I completely remove the seat, fender, console plates and fuel tank every fall on the tractor that I use for leaf cleanup.  Yes, I have a lot of leaf cleanup.  There is an unbelievable amount of debris that collects there preventing proper cooling and holding moisture causing rust.  I use engine cleaner and hose it clean, then oil all joints.  After that I can put on the snowblower and not worry about all that debris being wet from the snow.