more onan help needed

[6wheeler 669]

I finally got the engine back together on the 520. I am having an issue though. I started it up and it runs just fine. However, Houston we have a problem. It wants to take off full throttle. I cannot control it with the throttle lever. The cable works freely and throttle lever works just fine. If I pull back the governor arm it will Idle down just fine but when I release it? Up she goes. I did have to take the timing cover off to retrieve 2 of the valve retainers that found their way down the oil return port. I believe I put it back correctly so as not to disturb the governor. But, it has spring pressure on the arm. Not alot, but enough to make it throttle up. Did I miss something? If I just didn't need to idle down once in a while I'd leave it (just kidding). Thanks .  Pat

[Martin 2,133]

Sounds like the governor isn't assembled correctly, since you had the timing cover off I would say the pin in the back of the timing case isn't in its hole with the plastic ferrule correctly. Did you place the governor cup at the 3 o'clock position and line up the roll pin with its hole in the cup when putting on the cover?

[Martin 2,133]

You will have pressure on the arm. It should force the throttle fully closed when running. Arm should move freely one way when the engine is stopped and you should only feel the weight of the governor cup and balls when pushing it back the other direction.

[Theroundhousernr 590]

Dido to what Martin said. Also make sure that the little ball bearing that goes in the casting under the governor shaft did not fall out and roll underneath your work bench some where never to be found.....

[boomers_influence 106]

6wheeler

i believe your 520 should have a Nikki carb on it, # 146-0479. ( stamped on the throttle side )

if this is true, be sure that your throttle arm is in the REAR hole. ( closest to the crankshaft out put shaft )

thank you boomer ( the used onan engine parts guy )

[Desko 624]

Well anything because I'm having this same problem but I checked the pin and plug and there correct

[Martin 2,133]

an update would be great on this, even if you haven't ventured any further into the engine, we are all still learning and gathering information on how to fix problems and keep these engines running correctly....

[Desko 624]

an update would be great on this, even if you haven't ventured any further into the engine, we are all still learning and gathering information on how to fix problems and keep these engines running correctly....

Right!!

[motox25 36]

If all your linkages check out, might be time to crack the gear cover open again. Onan manual states if the cam gear pin is pushed in too far the engine will race under no load. Could also be a worn flyball, if any of them have developed grooves they will need to be replaced.

[6wheeler 669]

Thanks for all the info guys. Its been very busy at work. With getting 70+ hours a week I haven't had time to attack the 520 again, until today. Now here is an interesting development. I took the side cover off to start the governor dis-assembly again. When I unhooked the spring on the throttle linkage that goes from the governor arm to the carb and subsequently unhooked the spring that goes over the throttle rod? The governor works freely. I started the tractor with the spring unhooked and it works fine. I can move the governor arm and the engine revs up and idles down with the governor arm as it should. So, I think I had the spring hooked up wrong. But, I don't know where it should be hooked up to. I had one end on the carb. arm and the other hooked up to the governor arm. When I hook it up that way it puts spring pressure on the governor. Can someone help me as to where the dang spring hooks up to? I can't see a spot on the side cover where it could hook to pull the throttle back to idle position. This really shows how you can forget where things go when you have to leave a project in mid repair for awhile. Either that? Or I'm just losing it .   Thanks  Pat

[djohn24 10]

 Hi Pat,  could you get a picture loaded on here to show how you have it hooked up? That way, I could compare it to mine. I would load a pic to show you mine but, I don't know how to get it off my phone onto computer. As soon as my son gets home...I will get one loaded. This may help.

[Martin 2,133]

you shouldn't have any tension on the carb throttle when the engine isn't running. only the slight weight of the governor assembly should be there. the linkage from the governor arm to carb should move freely back and forth without much effort at all.

there is two types of link, one without the spring and one with the spring coiled around the straight part of the link. we are talking about the coiled spring here right?

heres how each end of the spring is hooked up. 

 

carb end

 

 

governor arm end

 

[6wheeler 669]

That is how I had it hooked up. So, Maybe I am not losing it . I will try to get the governor apart tonight. Funny though, when that spring is hooked up there is light tension on the arm and, no tension at all when un- hooked. Thanks again all for your help.     Pat

[boomers_influence 106]

club

the spring shown in martins last post IS NOT installed correctly.

on the carb end it goes to the OPEN hole. ( that hole, was never there before the spring was used )

on the governor arm the spring goes in the LITTLE hole. ( there again, that hole was never there before the spring was used )

thank you. boomer

[djohn24 10]

I wasn't having the issue 6Wheeler was having. Mine was lack of rpm's. I was only getting 2900 rpm at full throttle. I did adjust the throttle cable a little and was getting 3200 rpm. My linkage was hooked up the same as the pictures Martin had posted. So, I took Boomers advice on how to hook the linkage. I fired it up and opened to full throttle...I now have 3600rpm!!
Thank you Boomer!

[Martin 2,133]

I never noticed the Onan in the pics above to be low on rpm, now you guys have got me thinking if it would make a difference if I hooked it up the same way Boomer suggested. Guess I can try it and see. I only have one engine with this style linkage, the other is the earlier thicker linkage without the spring.

Sent from my iPhone using Tapatalk

[djohn24 10]

Martin, I did do something else I forgot to mention. The big spring that connects to the  governor  and over to the throttle cable bracket...I moved the spring on the governor arm one more notch over toward the engine. This seemed to put more tension on the governor arm. Mine is a 94. And if I saw your picture right, yours is a 94 also. If you were getting 3,600 rpm at full throttle without load. I'd let it go, By what I tried and with Boomers info....I went from 3,200 to 3,600 on the tach.

[Martin 2,133]

mine is a 95. i had a funny feeling that small spring wouldn't make that much difference........

if you moved the larger spring, that will change the sensitivity of the governor. heres an excerpt from the manual on the factory positions and what moving them either way will do.....

 

[tbarnhart 240]

The small spring over the governor to carb linkage doesn't really make that much difference in the speed or sensitivity.  It is there only to take the play out of the linkage and eliminate wear and a little surging. The adjustment of the governor arm to the throttle shaft and the position of the bigger spring attached to the throttle cable are what will make the difference in how the governor operates.

[djohn24 10]

 Thank you, TBarnhart & Martin. I have now developed another question. In my quest for more rpm's. I may have been wrong. The tach at full throttle was 2,900 rpm. With the adjustments made it's now hitting the 3,600. I was reading a Wheel Horse manual last night and in the specs area and it states...Max rpm...2,800 rpm. So, if anybody has any input on this that would be great!

[Martin 2,133]

all the P series engines in the Wheel Horse tractors were governed to 3600. Onan had many different applications and the engines were governed to the way the engine was used in that application. 

 

for our purposes though 3600 rpm is the magic number. what Wheel Horse manual were you reading that in?

 

here is the specs from the Toro Power plus manual 492-4006.

 

 

 

[djohn24 10]

3315-395EN 1991-94 520-He OM.pdf      Here is the manual I got the info from. Saying it's a 91-94 520 manual.


 

[Martin 2,133]

is this where you got this info?

 

 

maybe somebody here can explain why they even have this measurement here as its not needed to set the max speed on these engines. if it was set at this speed you wouldn't get your rated power from the engine. at the top of that page it says engine manufacturers rating at 3600, so why would you set it at 2800? here is the method in the manual...

 

[Theroundhousernr 590]

Some generator heads run at 2800. Less fuel consumption and less racket.

[djohn24 10]

Yes, that is where I got it.  I agree, doesn't make sense for the tractor. Would make sense for a generator like Theroundhousernr mentioned. It's clearly in reference to the Wheel Horse. Maybe some other Onan owners will jump in here to mention what rpm's they are running at. Oh Martin, I mentioned your engine as being a" 94" by the engine  Id tag in your picture above. Which I also have a 88 516H. However, the engine ID tag on that is 87. My 520H has a 94 on the engine ID tag and the ID plate on the tractor has been painted over and the previous owner tried to recover it without luck. I call my 520H a 94 but I'm guessing it could be a 95 also.