520h Onan Carb Questions

[leeave96 490]

I've got a mighty fine 520H, but I can't get the dang thing to start!

I've drained and put in fresh gas, checked the fuel lines/filter - they seem OK.

The engine will fire on starting fluid or carb cleaner, but won't continue to

run.

I haven't pulled the fuel line to check the fuel pump, but it looks like it is

pumping some fuel into the fuel filter between it and the carb. I'll check it

further tomorrow.

My question is - tell me about cleaning the Onan carb vs a rebuild kit.

I've read some stuff and it sounds like some folks clean their Onan carb from

time to time and save the expensive rebuild kit for another day.

What's involved in cleaning the carb vs a rebuild.

I've also read what sounds like - some folks are only taking the top half of the

carb apart? What does this do for you in terms of cleaning the carb and do you

have to remove the carb from the engine to do this - or to clean it for that

matter?

Thanks!

The other Bill

[nylyon-(Admin) 7,882]

If the 520 is the same as the 416, you can clean it while it's still on the machine. Take off the top and everything's there. There is also a drain plug which is situated perfectly for accessing the main jet of the carb. Remove the drain plug, insert the little tube and spray right into the jet. It's an easy job on the Onan's.

[Sparky-(Admin) 23,168]

If the 520 is the same as the 416, you can clean it while it's still on the machine. Take off the top and everything's there. There is also a drain plug which is situated perfectly for accessing the main jet of the carb. Remove the drain plug, insert the little tube and spray right into the jet. It's an easy job on the Onan's.

Thats some good info since mine started the "surge thing" while plowing today.

Mike.........

[nylyon-(Admin) 7,882]

That will help Mike, I have had to do it twice since owning it, and it's very easy to do.

[Docwheelhorse 2,740]

HI--cleaning the Onan carb is easy once you get the air filter off and such..... just make sure none of the little screws fall in. I had a 520-8 and had to frequently clean the carb due to surging at idle.... it would run great at full tilt (???). I got sick of it and sold the tractor...... Other than that the intake manifold has to be removed to remove the carb from the engine as the bolts for the carb come up from the bottom.

Tony

[smoreau 658]

If the 520 is the same as the 416, you can clean it while it's still on the machine. Take off the top and everything's there. There is also a drain plug which is situated perfectly for accessing the main jet of the carb. Remove the drain plug, insert the little tube and spray right into the jet. It's an easy job on the Onan's.

This is how I repaired the surging problem on my 520, Good post Karl

[leeave96 490]

Update:

Pulled the top of the carb and everything looked super clean, but I washed all down with carb cleaner. All passages were clear. I also took the cap off the side/bottom of the carb that covers the main jet and sprayed carb cleaner through it. That was clear too.

However, the fuel inlet on the carb from the fuel line hose seemed to be blocked. I put a piece of hose on it and blowed on it with some carb cleaner down the hose, and it became open. I also jiggled the float assy and that seemed to help too. I felt that when I put the carb back together, it was very clean/clear.

I cranked the engine and it ran for a second, then died. With a quick spary of carb cleaner, it would fire, then die again.

So I then took the fuel hose loose from the filter and blew on it and that passage was blocked again. I filled the hose with carb cleaner, but no fire.

BTW, the fuel pump works great and the fuel filter is not clogged in any way.

How should I proceed now with the clogged fuel inlet? I don't think it's the main jet? Should I put compressed air on it? If so where. If not, what next?

Any tips/suggestions would be much appreciated.

Thanks!

The other Bill

[leeave96 490]

Update:

I got the 520H going. The problem was the entrance to the carb was clogged - most likely by varnish. I disconnected the fuel line from the fuel filter at the top of the engine and filled it with carb cleaner and let a collumn of that stuff set there for a week. Today, I gave it a little puff of air with my mouth (bleeekk!!!) and it cleared. I then primed the carb from the same fuel line, hooked everything up and after a couple of cranks, the tractor fired up.

Thanks!

The other Bill

[Sparky-(Admin) 23,168]

Thats great news!

Glad to hear she's back in service.

Mike........

[zieg72 209]

If the 520 is the same as the 416, you can clean it while it's still on the machine. Take off the top and everything's there. There is also a drain plug which is situated perfectly for accessing the main jet of the carb. Remove the drain plug, insert the little tube and spray right into the jet. It's an easy job on the Onan's.

Thanks Karl, my favorite 520H just started doing it and my usual attempts did not clear it up. I will give it a go...

[leeave96 490]

_Update:

_{Had a little scare this late this afternoon. Went to start the 520H and nothing - dang! Checked the fuel line and it was again stopped at the carb entrance. I filled the fuel line upstream of the carb with some carb cleaner and let it set for a few hours and it started with the assist of some carb cleaner sprayed into the carb.}

_{That Onan engine might be a pain in the arse sometimes, but they sure sound great when they are hitting both cylinders!}

_{The other Bill}

[kpinnc 14,652]

If the carb is really gummed up, and it sounds like it is- it will still require taking it apart and cleaning it properly. It's true that a minor blockage can be removed with carb cleaner spray, but if it's really bad there is no substitute for soaking and cleaning. The good thing is that in most cases you won't need a kit.

[BMW Phil 0]

Run some Seafoam or similar through it- works wonders on stuff that's been sitting with crummy fuel in it.
And if you don't have an inline fuel filter, get one! The headaches it will save you are well worth the price!