520 h surges

[Black64galaxie 65]

 I just bought this 520 h.  I got it running and replaced the Stator and  regulator.  It seems to want to surge up and down I put some gas additive and ran it for a while and it still surges. Does the carburetor need to be taken off and cleaned out that's what I'm thinking. Or is it easier to just replace the car with a different one. Do I need to be careful taking off the exhaust manifold and intake manifold. I'm worried about breaking bolts  

Edited January 11, 2016 by Black64galaxie

[MalMac 1,332]

Sure sounds like a dirty carb to me. Your gonna need to get the top of that carb off and clean it out good along with all the passages. This is one of number one problems with a Onan surging. I am sure more Onan experts will chime in here. But that's the place I would start at.

[KC9KAS 4,744]

@Black64galaxie,  to

 

I see a Mustang, and your screen name tells me you are a FORD man!

[HokieAg07 129]

The Nikki carbs on Onans can be worrisome sometimes; its real common to experience engine surging with them which is a sign that a good cleaning is in order. You can remove the four screws on top and do a halfway cleaning which usually works for me most of the time but being that this is newly acquired, I would remove the entire carb and do a thorough cleaning. Exhaust comes off first then the intake manifold afterwards. Carb bolts go up from the bottom of the intake. Not a bad job at all. 

[lynnmor 7,825]

You could try just removing the carb top and cleaning as best you can.  If that doesn't work, then pull the manifold together with the carb  Inspect the manifold for leaks along the seam.  You shouldn't have bolt problems. but to be on the safe side, just crack the bolts loose and soak with PB Blaster overnight.

 

If you go this far, you might as well do it right.

 

Remove the exhaust and paint it with high temperature paint.  If you check the price of a muffler, you will do everything you can to protect it.

 

Remove the valve covers and adjust the valves.

 

Remove the engine tin so that you can clean the cylinder fins.

 

Use nothing but genuine Onan gaskets, the cheap ones will fail.

[Black64galaxie 65]

1 hour ago, KC9KAS said:

@Black64galaxie,  to

 

I see a Mustang, and your screen name tells me you are a FORD man!

Fer sher!

 

Thanks guys. Ya I figured that I would have to take off the carb and intake assy.  I was just worried about the bolts on the exhaust manifold. They look a bit rusty.  Don't want to have them break off into the block. 

[Ed Kennell 42,047]

1 hour ago, lynnmor said:

You could try just removing the carb top and cleaning as best you can.  If that doesn't work, then pull the manifold together with the carb  Inspect the manifold for leaks along the seam.  You shouldn't have bolt problems. but to be on the safe side, just crack the bolts loose and soak with PB Blaster overnight.

 

If you go this far, you might as well do it right.

 

Remove the exhaust and paint it with high temperature paint.  If you check the price of a muffler, you will do everything you can to protect it.

 

Remove the valve covers and adjust the valves.

 

Remove the engine tin so that you can clean the cylinder fins.

 

Use nothing but genuine Onan gaskets, the cheap ones will fail.

 

 

                                                 And if it still surges, clean the carb again . There are many posts on here detailing the cleaning procedure .  While  the tins are off, check for an oil leak under the oil filter mounting baseplate.   A small oil leak here will coat the cooling fins on the back cyl causing grass to collect and overheat the cyl.

Edited January 12, 2016 by ekennell

[Black64galaxie 65]

Thanks guys. Ya I figured that I would have to take off the carb and intake assy.  I was just worried about the bolts on the exhaust manifold. They look a bit rusty.  Don't want to have them break off into the block. 

[Bow_Extreme 550]

Tap the Exhaust bolt heads with a hammer and punch to help break them loose.  Some of the lucky ones around here have a special tool to hammer on which holds a socket to help break these loose.  I would highly recommend pulling the entire intake and carb.  Replace all the gaskets, clean and rebuild the carb, reseal the perimeter edges of the intake with ultra black RTV, and button that thing back up.  Should take a good night of working on it to get it back to running condition again.

 

Also, if your going to clean the carb and rebuild, replace the fuel line(pretty easy) all the way to the tank, replace the fuel filter, and drain and clean the tank.  This helps very much as there is a screen in the bottom of the tank that can be plugged with debris.

 

Going the extra mile usually pays off in the end.

[Black64galaxie 65]

40 minutes ago, Bow_Extreme said:

Tap the Exhaust bolt heads with a hammer and punch to help break them loose.  Some of the lucky ones around here have a special tool to hammer on which holds a socket to help break these loose.  I would highly recommend pulling the entire intake and carb.  Replace all the gaskets, clean and rebuild the carb, reseal the perimeter edges of the intake with ultra black RTV, and button that thing back up.  Should take a good night of working on it to get it back to running condition again.

 

Also, if your going to clean the carb and rebuild, replace the fuel line(pretty easy) all the way to the tank, replace the fuel filter, and drain and clean the tank.  This helps very much as there is a screen in the bottom of the tank that can be plugged with debris.

 

Going the extra mile usually pays off in the end.

Thanks guys. Ya I figured that I would have to take off the carb and intake assy.  I was just worried about the bolts on the exhaust manifold. They look a bit rusty.  Don't want to have them break off into the block. 

Yes I guess that's going to be the only way to get it to 100%.  It's been sitting outside by previous owner.  Can't understand people.  Take care of your stuff !!  

[whtractors24 3,373]

This is an easy job a jewelry cleaner / ultrasonic cleaner does dandy on these carbs  

[AMC RULES 37,196]

  Uh oh! 

Wait til the Mrs finds out Jason.  

 

 

Edited January 13, 2016 by AMC RULES

[Bow_Extreme 550]

41 minutes ago, whtractors24 said:

This is an easy job a jewelry cleaner / ultrasonic cleaner does dandy on these carbs  

I need to purchase one of these cleaners yet.  I have always wanted one.  I will have to put that on the short list.