520H test and tune

[sqrlgtr 2,198]

Finally got a chance to look at the 520H I brought home a week or so ago. Took breather off and safe to say PO probably hadn’t done to much preventative matainence. Taped throat up on carb and got rid of the big chuncks. Threw battery on and fired right up but has to have just a hint of choke on to not have a surge. All gauges and idiot lights seem to work but voltmeter shows just a little under 12 volts and when you unhook ground on battery it dies? Thought I would try some B12 in fuel before getting to serious on carb rebuild, might get lucky might but doubt it. Did drive around for a little while and man does that twin flat head hum no smoke knocks or weird nosies and has plenty of power. Trans seems good and stout but wants to creep backwards.

[ebinmaine 77,452]

11 minutes ago, sqrlgtr said:

carb rebuild

 

I've done one of these for @JCM  

Pretty straightforward.  

I did not remove the carb or reinstall though. I believe there's a procedure for the intake manifold.  

 

 

13 minutes ago, sqrlgtr said:

wants to creep backwards.

Hopefully just an adjustment.  

 

 

 

13 minutes ago, sqrlgtr said:

Did drive around for a little while and man does that twin flat head hum no smoke knocks or weird nosies and has plenty of power. Trans seems good and stout

 

 

Excellent! 

[ri702bill 11,310]

No worries - it just has its winter coat on...!!

 

[JCM 10,774]

A few pics for you. The 520's seem to be the most abused of ALL WH tractors out there. Why. I have no idea. Keep at it, you will get there.

[Handy Don 15,988]

55 minutes ago, sqrlgtr said:

when you unhook ground on battery it dies?

On non-magneto tractors, the battery powers the coil for ignition. The current goes out of the battery via the “red” wires and to the coil. If you disconnect the battery ground, those poor little volts cannot find their way home to complete the circuit!

Edited Thursday at 10:58 PM by Handy Don

[lynnmor 8,642]

How many hours are on the tractor?  It may be due or overdue for a valve adjustment.  If it has over 750 hours on it then adjusting the valves is due and doing that will have you pulling the exhaust and intake which is a good time to do a carburetor cleaning and some other needed maintenance.  Do not continue to run the engine hard with a lean mixture caused by a dirty carburetor unless you want to join the loose valve seat club.  Let us know if you want to do a proper valve adjustment and carburetor cleaning and we can outline the needed work.

[Handy Don 15,988]

1 minute ago, lynnmor said:

unless you want to join the loose valve seat club

Lynn, you've given me an idea for some more clubs!

Stuck Hub

Stuck Steering Wheel

Stuck Hitch Pin

No Balance Gears

Patina

and many more...

 

[sqrlgtr 2,198]

26 minutes ago, lynnmor said:

How many hours are on the tractor?

A little over a 1000 and supposed to be correct???

 

28 minutes ago, lynnmor said:

Let us know if you want to do a proper valve adjustment and carburetor cleaning and we can outline the needed work.

Yeah main objective today was just run it around a bit just to see what I did have, believe everything is pretty solid and she just needs a little TLC. Ordered carb kit today and plan was to take top off carb and clean up best I could but agree valve adjustment wouldn't be a bad idea. What gaskets and stuff would I need to have on hand before I tackled a valve adjustment? I was also surprised at the ground speed it had. Seems a lot faster than a 6/8 speed tractor to me. Hydraulics seems real stout also. From the looks of the turf on that carb, I can't imagine what the cooling fins looks like .

[kpinnc 17,227]

2 hours ago, sqrlgtr said:

little over a 1000 and supposed to be correct???

 

At that point you need to decarbon the heads anyway. To get there, the intake manifold and exhaust will have to be removed so a valve adjustment is easy at that level of disassembly. 

 

But- a properly cared for Onan can last literally thousands of hours. It's worth it. 

[Ed Kennell 44,965]

While you have the tins off, Please replace the gasket on the oil filter base plate.    I have found several of these seeping a small amount of oil that gets blown across the rear cooling fins causing the grass to stick and clog the fins.   I use a spray contact cement to glue the new gasket to the base plate to insure it remains in position on the very narrow sealing surface.  Don't forget the rubber grommet that seals the oil filter to the tins.  

[mrc 1,056]

you might want to ventilate the belt guard too.   in the wh application the belt guard blocks a LOT of hot air from escaping.

[WHX?? 55,144]

15 hours ago, JCM said:

The 520's seem to be the most abused of ALL WH tractors out there. Why. I have no idea.

So true Plunge. 

[lynnmor 8,642]

14 hours ago, sqrlgtr said:

A little over a 1000 and supposed to be correct???

 

Yeah main objective today was just run it around a bit just to see what I did have, believe everything is pretty solid and she just needs a little TLC. Ordered carb kit today and plan was to take top off carb and clean up best I could but agree valve adjustment wouldn't be a bad idea. What gaskets and stuff would I need to have on hand before I tackled a valve adjustment? I was also surprised at the ground speed it had. Seems a lot faster than a 6/8 speed tractor to me. Hydraulics seems real stout also. From the looks of the turf on that carb, I can't imagine what the cooling fins looks like .

 

Sounds like you ordered a cheap Chinese carb kit, I would use only the bowl gasket and the rest may be junk. 

 

Before disassembly check the compression, if it is higher than normal pull the heads and decarbon, if too low you might want to refresh the valve and seat surfaces.  If you pull the valves, replace the intake valve seals.

 

Use only genuine Onan gaskets, I have had cheap intake gaskets turn to mush in a year.

 

You will need intake, carb mount, exhaust and valve cover gaskets.  Possibly need head gaskets, oil filter mount gasket and of course the oil filter grommet that the last owner tossed.

 

The exhaust is expensive to replace, so glass bead it and paint with Rustoleum High Temperature spray paint.  The valve covers often rust so paint them with engine paint.  I use satin black engine paint on heat shields and all other engine tins.

 

The intake manifold needs to be checked for leaks and if that needs repaired check back.  You can test by clamping a plate with gasket over the carb mount area and fill the manifold with diesel fuel.  Look for notches worn in the edges of the manifold where the heat shields might have been contacting, correct by grinding some clearance in the shields.

 

You will need a 1/4" and 3/8" drive torque wrenches.  All bolts should have a drop of engine oil on the threads, do not over-tighten any of them.  Download the Operators Manual and the Onan Service Manual.

[Brockport Bill 2,225]

Had a surging onan 20, did carb rebuild and manifold gasket which solved the surging. 

[kpinnc 17,227]

2 hours ago, Brockport Bill said:

Had a surging onan 20, did carb rebuild and manifold gasket which solved the surging. 

 

 

Rebuilt a carb for the same, no change on two different Onans. But a tiny bead of silicone on the intake manifold seam cleared up all of the surging.