Onan 20 horsepower surging from 87 520- HC

[Jeanennes Ride 3]

Hello everyone, could we get your help to a common issue with a question mark answer. We just got in a 5:20 H - c. It is less than 800 hours. It has a surging problem that starts as soon as you load it down and mow. This seller is very good and tried to fix the problem and we are stumped. The carburetor is replaced with a new one, manifold gaskets changed, fuel pump changed. It looks good for oil and air filter. Repositioning the selection for the governor improved it somewhat. I know that most people have a problem with the carburetor and cleanliness or the manifold gaskets. I don't know and we'll let you know as soon as he gets back to me on whether this has a split manifold. I think it does. As I am in a power chair and paralyzed I can't get up and see things like I would like so I have to depend on others to tell me what they have done and what they see. When it does run without the surging it seems real good and even and steady. I think it's sat for a year from the time that it was running good. I will check to see if he changed the gasoline out of it but I'm not sure on that. Is there anything electrical that could cause this like points or coil maybe getting weak.? Is there any possibility that the magnet on the flywheel could be getting weak and creating a weak spark?. We love this tractor and think it's going to be really good for Janine and I'm so happy for the Forum and the support and camaraderie of the Good Wheel Horse people. I'm only about 40 miles away from South Bend Indiana where they built these things. So sad they couldn't keep building them and make them well like they did the old ones. Any comments or suggestions would be greatly appreciated

[JCM 9,169]

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[lynnmor 7,307]

 

It sounds like you have an understanding how things work.  Usually the surging issue is caused by carburetor problems, but it has been replaced.  Be sure that the rod between the carburetor and the governor is installed correctly, it should be in the center hole on the governor arm and the rod should be in the first bend.

 

 

It will have a split manifold and the carburetor installer should have inspected it.  Heat shields can cut a groove in the edge of the manifold so look for that.  The engine uses electronic ignition so no points, that system can become sensitive to heat and stop sparking but that doesn't sound like your issue.

 

You are on the right track about the gasoline, simply discard all old fuel and use fresh.  It would be a good idea to replace all fuel lines and filter, perhaps the new carburetor was fouled immediately by rotting fuel hose.  You will find that most on here prefer to clean original carburetors and stay away from cheap imported ones.

 

 

 

 

 

Edited July 19, 2023 by lynnmor

[Ed Kennell 38,186]

 to the 

 

All sound advice from Lynn.   My limited experience with the few 520s I have owned showed the surging was due to dirty carbs.     One poorly maintained 520 that surged badly took three carb cleanings before to stopped surging.

[lynnmor 7,307]

I want to add that your early model may not have that "shepherds hook" style linkage shown at the bottom right of my above photo.  If it has only one simple bend, disregard the suggestion about the correct bend.

[Jeanennes Ride 3]

So first of all I wanted to tell you guys in the community how grateful I am for your help and the kind of good people that you are. Also understand that for Janine this is something that she can do and will give her some purpose for her day and she is very excited to have something in the future to look forward to. She has MS and it's a long story but this is a really big big thing for her. I was a beginning organic farmer and got hurt by a bowl and had my neck broken. The Quest for truth and knowledge is never so apparent till you lose everything and you are in the system that we're at. That is what I like about Wheel Horse you know what you're getting and it's quality and I love that. The tractor we got from a gentleman who has many of them and he said this one never did run without the surging issue and I guess he got it about a year or two ago but before he sold it to me he did change the gasoline and did not know any breakdown of tubing. He is going to come over and we are going to look at that manifold and see if we can find out what's going on. Does anybody know why Onan split the manifold and is there a gasket to be replaced or is there a sealer that is good to use? Years back I know I had used silicon later to find out the gasoline broke it down and it ran like Snot in the engine. So on oil systems I'm okay with our TV. But anything gasoline I think about all I ever used was a Permatex shellac kind of compound. Sorry if things look a little messed up on the writing. I'm using talk to text since I can't use my hands. Thank you for the wonderful pictures and explanation about the linkage. I will get back to everybody as soon as seller Dave comes back to help us figure it out.

[lynnmor 7,307]

At the top of the Engines topic there is information about the intake manifold repair.  Basically you drill out the rivets and replace them with tiny bolts one at a time.  I use Motoseal 1 for the sealer.  Only a small percentage of manifolds need the repair.  I would check the compression first thing to see if the engine is healthy, you have done much of the basic work and you don't want to keep beating a horse if it is dead.  Ethanol in gasoline shortens fuel hose life but there is ethanol resistant hose available and probably most of it today will be that type. Keep coming back with new information, we are here to help.  Your writing is fine, if you can include photos they are worth a thousand words.

[Jon Paulsen 290]

12 hours ago, Jeanennes Ride said:

Does anybody know why Onan split the manifold and is there a gasket to be replaced or is there a sealer that is good to use?

I drove up to the big Ford dealer up there in Warsaw and bought a new Grand Marq... a long, long time ago. Now I'm in about the same boat as you, but I am lucky I can drive far enough to see my mom in Rensselaer and get to and from work most of the time. I think I'm an hour and a half SW of you. Been here for decades. 

 

Anywho, all the above good info. IDK why they split it other than ease of manufacturing maybe. Toyota did that with the old Land Rovers and the two halves were a matched set and very expensive at the time. Then when something failed it burnt a hole in the bottom half. So some fellas bought a bottom half or two and filed to fit. Don't remember what the details were except they stopped laughing at my never stuck Jeep J-10 

 

I posted a pdf about rebuilding the twin's manifold. I found it here and thought I had bookmarked just a week or so back. My brain is foggy from the smog we had come in from the fires up north, but will try to find it. 

Edited July 20, 2023 by Jon Paulsen

[Jon Paulsen 290]

The PDF is in the thread linked above. I was ill when I found it and did not read it and have never really worked on my Onan. It has some good pictures and the thread mentions some glues that work and I think the PDF does as well. 

Edited July 20, 2023 by Jon Paulsen

[Jeanennes Ride 3]

On 7/19/2023 at 12:45 PM, lynnmor said:

At the top of the Engines topic there is information about the intake manifold repair.  Basically you drill out the rivets and replace them with tiny bolts one at a time.  I use Motoseal 1 for the sealer.  Only a small percentage of manifolds need the repair.  I would check the compression first thing to see if the engine is healthy, you have done much of the basic work and you don't want to keep beating a horse if it is dead.  Ethanol in gasoline shortens fuel hose life but there is ethanol resistant hose available and probably most of it today will be that type. Keep coming back with new information, we are here to help.  Your writing is fine, if you can include photos they are worth a thousand words.

 

[Jeanennes Ride 3]

To everybody who replied thank you very much. I am new to getting my way about this forum so please forgive if I'm not doing things quite right. And I also wanted to reach out to John there and say.. I can't remember cuz everybody says Semper Fi and that's the Marines and anyway I am a squid just like you. USS Houston SSN 713 fast attack submarine out of San Diego with the tomahawk cruise missile program. Fortunately or unfortunately I gave my time right after high school and 17 years old and I was in the Navy for 6 years and 8 months. So we are making progress towards finding out with the issue is with this 520 and we have a plan of attack. By the way I had seen a post from Boomer who is I guess from Minnesota and I got his email and wrote and I also left two phone messages but have not had a return of any communication. Is it possible that he is in bad health? I know he would have been a great resource to talk to. So if anybody knows please let me know. Had talked about being able to get another manifold fairly reasonable. I spoke to David I believe it was day before yesterday and he went to the local Amish small engine repair place who knows quite well about the onions I guess. They seem to think that there might be a reason unheard of for the cause for the surging related to the governor and something that they would have to put a pin in for. So I'm not understanding it or even able to speak intelligently about it but they seem to think that that could cause that issue also. Anybody know about that? So I see so many posts out there from people warning about the ethanol which I absolutely knew about and know about. My question though is I have been hoping to avoid it by buying High test fuel. As it have ethanol in it or do you have to look on the pumps on it I know it was stated on there. Since I don't get out and somebody else has to get it a gas can at a time all I can say is not no ethanol but I'm not up to date with another just not putting it in nowadays and not really writing it on the pump anymore. My first experience with the ethanol was in a I think 81 Saab 900. It was a wonderful car and one day it stopped running. And for whatever reason I had got some kind of an idea that I was starving for fuel and I put in more fuel and filled it up fully and it ran again. Those old Saabs were wonderful. They had the fuel pump access on top of the gas tank underneath the floorboards literally. So you pulled up the floorboard and undid a big rubber thing about 8 in in diameter with a hose clamp and the whole fuel pump and sender was right there I pulled it out of the tank and it was all goo. Anyway I had to get something else for all the rubber stuff that was gone but I learned the hard way about ethanol. Okay I should probably be more brief about things but thank you everybody and if you have any ideas or answers about my questions please if you could share. Thank you Robert and Janine

[lynnmor 7,307]

While ethanol only exists to buy votes from the corn producers, it isn't as big of a problem that many on here think.  Nearly all gasoline contains 10% ethanol and I have used it in all my tractors, mowers and cars.  High test gas might contain even more ethanol, you can only find ethanol free at a station that clearly states ethanol free, see Pure Gas to find a station near you.

 

Please do that compression test so we can move forward on this matter.