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Kurt-NEPA

My 520H has gone hunting - needs some help

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Kurt-NEPA

 

On 5/20/2016 at 8:32 AM, WHX61/3 said:

Sorry for hijacking the thread Kurt! :)

 

No worries WHX61/3

 

I just ordered the parts for my project.  Stay tuned!

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Kurt-NEPA

Update,

 

With the gaskets ordered, I moved on to carb cleaning.

 

I pulled the manifold and separated the carb.  Then took the carb apart as much as I could.  I went through each opening with carb cleaner, then a copper wire, then carb cleaner again.  Nothing seemed blocked.  So the carb went into the can of carb cleaner.  I will repeat tomorrow and daily until the gasket get here.  Probably 3 or 4 days.

 

The good news was that I had this all apart about 20 hrs. ago and had coated all the threads with anti-seize. Made it easy to take apart this time. But what a PIA it is to get to the point where you can separate the carb from the manifold. 

 

Stay tuned, thanks for the help.

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Kurt-NEPA

Another update.

 

I soaked the carburetor for two days in a can of carb cleaner.  It looked as clean as a new one when it came out.  I blew out each passage with compressed air and then again with carb cleaner.  I also replaced the valve/screen on the bottom of the gas tank.  The old one looked dirty and was partially collapsed.  Also, all the rubber fuel lines, gas filter, and the vacuum line to the vac gauge were replaced.

 

With fingers crossed, I put it all back together and started it back up.  I warmed it up tried to mow a bit.  Within 5 minutes the hunting was back.  Ugh! - No improvement

 

So I moved on to the next phase and replaced the ignition switch.  The connector looked OK.  I started it up and mowed and the hunting came back, but it was greatly improved.  I added some Sea Foam to the gas and mowed for about 15 minutes and I think I noticed some more improvement.

 

At this point, I think I'm going to run it for a few weeks and see what happens.  If I can find a new plug for the ignition switch, I'll replace it.  No 9 pin connector on the 1988 520H, so that is not it. I will be checking all the other connections.

 

The only other thing I did before this all started was to replace the oil and filter.  I couldn't get 30wt synthetic, so I used 10W-30 Mobil 1.  I can't believe that could cause all of this.

 

I'm running out of ideas.

 

Thanks for all the help,

 

Kurt

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cleat

Well, my 520HC started doing exactly as you described. It would run perfect then as I was mowing, it would start to hunt.

 

Carb perfectly clean, and I have been using this machine for the last year for just moving trailers around in the summer and plowing snow a little in the winter. Never mowed with this unit since I got it and rebuilt it. Since I just built a 48" deck, I installed it on this machine to test both the deck and tractor out.

 

Never hunts when not mowing, that must get things hotter.

 

I noticed at this point (when the hunting starts) that the fuel filter was empty, and there were just bubbles coming in on the inlet.

 

I had a spare fuel pump so I swapped it out and the filter filled right back up and I proceeded to mow.

 

For a while anyways, then the surge came back.

 

Drove back to the garage where I noticed the filter empty again and bubbles feeding into it.

I also just happened to notice gas line was laying directly on the oil filter.

 

Moved gas line to the other side of the negative battery cable which put it at least an inch away from any direct engine heat and finished mowing the yard.

After almost an Hour of running, the filter maintains a liquid level not full but a good 1/4 and the engine ran smooth all the way through.

 

I believe that the fuel line was getting hot on the filter in combination with the fuel pump pulling a vacuum on it causing a vapour lock at the pump.

 

Next time I mow the lawn I will see what happens.

Edited by cleat
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Kurt-NEPA

Interesting Cleat.  As I was testing mine out this afternoon, I noticed the filter was less than half full.  I decided to go back to the electric pump and try that.  Now the filter is 3/4 full.  My surging has improved a bit.  I would now say its is minor, but noticeable.

 

I'm wondering if maybe the fuel filter could be part of the issue.  I put on a Kohler filter that I can get locally.  Maybe a Toro filter is somehow different.  I might by-pass it for a test and see what happens.  I'll re-route the hose while I'm at it.  Worth a try.

 

I keep thinking that I'm missing something simple.

 

Thanks,

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budman2

I know that this sounds too simple but when mine does that surging crap I just take an air hose and shoot a couple of blast of compressed air down that small hole in the carb throat! it works for me! hope this helps budman2.

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cleat

Be careful with too much compressed air.

 

I managed to blow the Welch plug out of one once and had to replace it.

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Kurt-NEPA
8 hours ago, budman2 said:

I know that this sounds too simple but when mine does that surging crap I just take an air hose and shoot a couple of blast of compressed air down that small hole in the carb throat! it works for me! hope this helps budman2.

 

Worth a try, nothing else seems to be working. I'll take it easy.

 

Thanks

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WVHillbilly520H

Those fuel filters are pretty much "generic" but instead of Toro it's ONAN(made in Israel) but the STENS brand is universal for Kohler,Onan & Briggs ect and works for 1/4" or 5/16" lines and works just fine also you may want to run a "colder" plug I can't remember off the top of my head  :think: if lower or higher numbers for Champion factory is RS17YX so 16,15 ect had 12s in the 95 I just bought just my :twocents-02cents:,Jeff.

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Kurt-NEPA
46 minutes ago, WVHillbilly520H said:

you may want to run a "colder" plug I can't remember off the top of my head  :think: if lower or higher numbers for Champion factory is RS17YX so 16,15 ect had 12s in the 95 I just bought just my :twocents-02cents:,Jeff.

 

Interesting comment on the plugs.  I can easily try some other plugs and see what happens.

 

I don't really think the fuel filter would have anything to do with this unless it was plugged.

 

Thanks,

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lynnmor

The air in the fuel filter is a non-issue, they all do that.  Spark plugs either fire or not, the heat range will determine how much fouling might build up.  I've had a welch plug fall out of a carb and that caused serious hunting when not under load.  Blowing compressed air in might collapse the float or blow out the welch plug, I wouldn't do it.  The carb needs to be cleaned properly, and that might mean removing the welch plug and then replacing it.  Holding the straw of a can of parts or carb cleaner in each orifice is a good way to blast out dirt.

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WHX??
14 minutes ago, lynnmor said:

The air in the fuel filter is a non-issue, they all do that.

 

I agree with lynn sometimes mine are plumb full sometimes but sometimes  they only have a little but the motor run fines regardless. I usually run the clear Fram g2 or g3's

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Kurt-NEPA

I've been running with air in my filters for years, so I don't think that a problem.  When I put an electric fuel pump on my other 520H (1995), It managed to fill up the filter, but it made no difference in the way the engine ran.

 

On this surging 1988 520H, I've been making some progress.  The surging has diminished, but its still there.  At least I can mow with it.  At this point I think the Sea Foam is doing some good.  When I cleaned the carb, I did not pull the Welsh plug, so maybe I missed something behind it.  I am still convinced that I have something plugging a passage in the power circuit of the carb.  Strange part is that is variable.

 

Thanks for all the comments

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Kurt-NEPA

Yet another update.

 

I've been running my 520H hoping that Sea Foam was going to cure the surging under poweer.  The surging had subsided to a noticeable level.  Annoying, but I was able to mow.  I was living with it, but it was not getting better.  This morning the surging seemed to be worse.

 

So I pulled the carb yet one more time.  This time I ground a screwdriver and removed the main jet and cleaned everything.  I was really hopeful, but I had not improvement.  Since I was low on gas, I refueled with non-ethanol premium gas.  The big Onan seemed to run better, but the surging was the same. 

 

I was running out of ideas, so I decided to check the governor settings.  The 520H governor arm has three holes to governor control arm.  Mine was in the center.  I checked it according to the manual and the procedure said it should be in the inboard hole.  So I moved and tried the tractor,  The surging got much worse.  Scratching my head, I thought why not try the outer hole.  Surprise, Surprise my surging in GONE.

 

So I declare Victory,  At least until I go down this path again,

 

Thanks everyone for all the help,

 

Kurt

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cleat

Sounds like you have it set close according to my manual.

 

Governor.pdf

 

I have all of mine in the second last hole. I tried the very end hole on the HC and it would sometimes bog a bit when accelerating via the hydro and mowing grass. I think the governor was just a little too insensitive at this point.

 

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Kurt-NEPA
1 hour ago, cleat said:

I have all of mine in the second last hole. I tried the very end hole on the HC and it would sometimes bog a bit when accelerating via the hydro and mowing grass. I think the governor was just a little too insensitive at this point.

 

 

In looking at how this governor linkage works, I think the spring is counteracting the fly ball action.  The difference is what adjusts the carb. There are two adjustments. 1.) Spring position on the tension lever, and 2.) the throw from the the governor lever to the the carb.  I just changed the governor to carb throw.  That might not be the right thing to do.  The spring position is now set at the 4th hole out.  I think I'm going to play with the spring position and see what happens.  My thinking is that the spring in the 4th position (last) might have been the real cause.

 

The manual is less than clear on the spring adjustment (or I just haven't found it yet).

 

Fun!

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