520H (late 80-early 90s)

[AHS 1,440]

9 hours ago, lynnmor said:

Idle speed is to be 1200 RPM and maximum throttle is 3600 RPM.

 

To adjust carburetor and governor do this:

Back off the idle speed screw, located near the throttle cable towards the front of the engine, about 2 turns.

Adjust the idle stop screw, located on the rear side of the carburetor, to 1000 RPM.

Adjust the idle mixture screw for the highest and best idle and readjust the stop screw as needed to maintain 1000 RPM.

Repeat the last step as needed.

Adjust the idle speed screw to 1200 RPM.

The above procedure will give you a governed idle.

Move throttle to full, the speed should be 3600 RPM, bend throttle stop if adjustment is needed.

 

Use genuine Onan intake gaskets, some cheap imports turn to mush quickly.

Ok, thank you for the information! Wow! Im going to replace the intake gaskets. The carb is right there, might as well rebuild it?

[lynnmor 7,306]

3 hours ago, AHS said:

Ok, thank you for the information! Wow! Im going to replace the intake gaskets. The carb is right there, might as well rebuild it?

The word "rebuild" is tossed around a lot when they most often just need cleaned out.  Yes, I would clean out the carburetor since you will have it off to replace the gaskets.  I have used cheap bowl gaskets from eBay kits but the needles and manifold gaskets were junk.  Often the original bowl gaskets can reused.

[AHS 1,440]

4 hours ago, lynnmor said:

The word "rebuild" is tossed around a lot when they most often just need cleaned out.  Yes, I would clean out the carburetor since you will have it off to replace the gaskets.  I have used cheap bowl gaskets from eBay kits but the needles and manifold gaskets were junk.  Often the original bowl gaskets can reused.

It runs alright; for being old gas and spark plugs. When i raise the throttle rapidly, it tends to die off a bit before going to wide open throttle. That could be intake gaskets and old gas?

[lynnmor 7,306]

2 hours ago, AHS said:

It runs alright; for being old gas and spark plugs. When i raise the throttle rapidly, it tends to die off a bit before going to wide open throttle. That could be intake gaskets and old gas?

Or that stuff that you should remove from the carburetor.

[AHS 1,440]

@lynnmor yup, that could be as well. I’ll take a look thru the carb and see what needs replacing.

[AHS 1,440]

Are the gauges on the 520 supposed to light up? Im trying to get the tach to work. 

[Handy Don 12,232]

1 hour ago, AHS said:

Are the gauges on the 520 supposed to light up? Im trying to get the tach to work. 

Illuminate in the dark, as with headlights? No.  Some gauge housings I’ve seen had a plugged port which could hold a lamp & socket but I’ve never seen any with lamps installed.

In the wiring diagram you can see that the tach needs both power (pink?) and the pulse feed (which comes from the engine via the 9-pin; gray?)

 

Edited March 10 by Handy Don

[lynnmor 7,306]

1 hour ago, AHS said:

Are the gauges on the 520 supposed to light up? Im trying to get the tach to work. 

I know that 1991 and up had lamps in the gauges and they were always on with the ignition switch on.  After looking at your wiring diagram I'm not seeing those lamps.  The illuminated gauges have a rubber bulb socket pushed into a hole in the back side.

 

The tachometer gets its signal from a gray wire that is attached to one of the outer terminals of the voltage regulator.  It also needs a + & - connection.

[cleat 5,995]

1 hour ago, lynnmor said:

I know that 1991 and up had lamps in the gauges and they were always on with the ignition switch on.  After looking at your wiring diagram I'm not seeing those lamps.  The illuminated gauges have a rubber bulb socket pushed into a hole in the back side.

 

The tachometer gets its signal from a gray wire that is attached to one of the outer terminals of the voltage regulator.  It also needs a + & - connection.

As lynmor said.

The gray wire goes onto the terminal closest to the battery, you can just see it in this pic.

 

[kpinnc 12,061]

3 hours ago, Handy Don said:

Illuminate in the dark, as with headlights?

 

My 1990 lights up anytime the tractor is running. There is a lamp plugged into the back of every guage except the hour meter. 

[AHS 1,440]

6 hours ago, kpinnc said:

 

My 1990 lights up anytime the tractor is running. There is a lamp plugged into the back of every guage except the hour meter. 

So, the lamps can be replaced? Ive figured out the gauges cluster issue, i think (I haven’t started it yet). The 12V wire was grounded on the tach. All my gauges work. The headlights switch needs to be replaced…. Getting there!!!

[AHS 1,440]

@cleat A+ &-? Did you mean power and ground? I’ll have to see on voltage regulator if the gray wire is hooked up. The wiring all look factory, except for the parts that the former owner touched!

[AHS 1,440]

Does that look like it has lights? How do they come out?  I swore I saw lights! 

[cleat 5,995]

The early 520's with the SW metal body gauges did not come with lights installed.

They would go where the big round metal plugs are.

 

When you turn the key on without starting the engine the tach should go to zero right away proving it is getting power.

 

You should also see the fuel gauge go to the correct level and the volt gauge go to whatever voltage your battery is at.

 

[lynnmor 7,306]

2 hours ago, AHS said:

@cleat A+ &-? Did you mean power and ground?

Yes.

[Horse Newbie 7,069]

On 3/7/2024 at 11:17 AM, kpinnc said:

 

You mean there are rules to all those colors? 

Like a coloring book… it’s a free-for-all !

[Handy Don 12,232]

2 hours ago, AHS said:

Does that look like it has lights? How do they come out?  I swore I saw lights! 

So yeah, as @cleat noted, remove those round plugs and those gauges are “lamp compatible."

Good luck finding lamps & plugs, though! (And if you do, one side will go to the “pink” instrument power wire and the other to ground.)

[Horse Newbie 7,069]

5 hours ago, AHS said:

The headlights switch needs to be replaced

On my 1994 520H, when the headlights switch did not work, I had removed it with the intention to replace.

But being the way I am, I started cleaning the switch, spraying a liberal amount of WD-40 in( down in between the rocker switch piece and the switch body ), and all around the switch .

Worked the switch on and off about 10 times, blew it out and off good with compressed air, and it’s been working fine for about 6 years now.

If you end up replacing the light switch, I have heard on here that you can find the correct on to snap back in the dash at some places like O’Reillys, Advance Auto, NAPA, or Auto Zone…

Edited March 10 by Horse Newbie

[Horse Newbie 7,069]

I don’t believe anyone has mentioned it yet, but I would recommend cleaning all spades and terminal ends with sandpaper or a wire brush-the whole tractor, not just the ones you touch. Then coat with dielectric grease.It may save you from having another electrical problem next week, or next year.

[cleat 5,995]

30 minutes ago, Handy Don said:

So yeah, as @cleat noted, remove those round plugs and those gauges are “lamp compatible."

Good luck finding lamps & plugs, though! (And if you do, one side will go to the “pink” instrument power wire and the other to ground.)

 

Or connect them to the green headlight wire so they are only on with the lights saving the bulbs from being on all the time.

 

[Horse Newbie 7,069]

You may be able to find light sockets, and who knows, you may be able to find led compatible socket's.

If you wind up using the socket’s that take the old “insert and twist” type incandescent bulbs, when you get bulbs, the bulb actually, I have found come in two sizes( the glass part) make sure you get the smaller design. The larger design will melt a plastic housing.

Edited March 10 by Horse Newbie

[AHS 1,440]

I’m 99% sure my tach is junk. My pink is at 12V, my ground is connected to ground, my signal wire is connected to the voltage regulator. I know this is newer than mine. Can you take a picture of your newer 520H, and i can copy the wiring?

[Handy Don 12,232]

2 hours ago, AHS said:

my signal wire is connected to the voltage regulator.

if you have a DVOM with a frequency range, you can test the pulse feed on the line coming into the tachometer. The exact frequency you observe isn’t important (it’s based on the number of coils in the stator and the RPM of the engine; faster engine=>higher frequency) but you’ll at least be able to see if there ARE pulses!

[Horse Newbie 7,069]

2 hours ago, AHS said:

Can you take a picture of your newer 520H, and i can copy the wiring

Who are you asking to take a pic ?

[cleat 5,995]

I believe you will get a reading using an AC voltmeter between the signal terminal and ground.