Onan Governor Sensistivity

[Jake217 20]

Hey All,

 

I'm at my wits end on setting the governor for my Onan P220G that's on my 88 520H.  I did an engine refresh last year ( rings, guides, valve seals, hone, etc.).  Everything as far as clearances are in spec.  Valves are dead on.  Seats are tight.  The carb is probably the cleanest thing in my house - soaked for a week in new carb cleaner bucket, all orifices blown out, new carb mounting gasket and manifold to spacer gasket.  I checked throttle shaft end and side to side play and it is negligible.  I also coated the entire seam of the manifold with copper form-a-gasket trying to figure out what's wrong.  I've done the propane and spray Gumout tests looking for a manifold vacuum leak and found nothing. The engine runs fantastic at any throttle position.  No hunting or surging. 

 

My problem is that any time I goose the throttle ( idle to full throttle real quick) the engine over rev's off of the tach scale (around 4500 RPM) for a split second, then corrects itself and settles in at a nice 3550 RPM which I have adjusted the throttle stop and throttle cable to get there.  I have not used the tractor at all since the refresh due to the unpredictability how the engine will react under load.

 

I have studied the Onan manual on sensitivity till my eyes blurred and I've searched all of the forums I could find on Onans. I figured that by increasing the sensitivity I would get the governor to react quicker and catch the over rev situation earlier.  No dice.  I've now run out of holes on the governor linkage as far as increasing the sensivity.

 

I also thought I might have a venturi vacuum leak vs. a manifold vacuum leak since venturi vacuum increases as throttle increases and I'm getting too much air, but all looks good. Throttle plate looks tight, shaft to carb body seems OK.  

 

I also replaced the governor spring last week thinking 26 years might have stretched it a bit, therefore not reacting fast enough. No joy.

 

Any ideas, cause I'm baffled... thanks for any help.

[Martin 2,130]

I think you have a slipping plastic spacer (the one with 5 fingers that spaces the flyballs) on the end of the camshaft gear.  the plastic gears can slip on the end of the camshaft, and they sometimes don't have a 'key' into the cam gear. they can come loose and slip instead of holding tight and doing their job holding the flyballs in position and making the governor perform how it should.

 

more info here......

 

http://www.mytractorforum.com/showpost.php?p=1474679&postcount=95

Edited February 21, 2014 by Martin

[Jake217 20]

Thanks a million, Martin.  What you said makes perfect sense.   The last thing I want to do is pull that engine out again, so I may try to do it on the tractor; don"t know 'til I take a look.  Just need to see what's going on.  I'm assuming that if that spacer pops right off the camshaft, then that was the problem.  Any idea of when Onan started putting keyed spacers on the cam gears?  It seems that the keyed spacer would stop the slipping problem  That post you noted is very good. 

 

Thanks Again.

[Martin 2,130]

im not sure when they used them and when they didn't. i have only had 2 of them apart, a p216 and p224 (t260), the 16 didn't have the key and was plastic, the 24 had a steel one with the key. the link i posted shows a plastic keyed one. you want them to be a tight fit, but its a pain to remove a tight one if you are rebuilding. the best way to remove is always how was mentioned in the post (that is if you don't want to damage it.) I've had to help one with a soft lever , just way too hard on the hands to remove. the keyed one seemed to be easier. 

 

every component has to be in working condition for the governor to work as it should. you want the finger spacer tight, the fly balls need to be smooth and round, the back of the governor cup needs to be smooth, the measurement between the cup and end of pin at the retainer needs to be at spec (pin depth in end of camshaft is very important). theres a lot of stuff that needs to be right. oh, and the locator pin in the back of the gear case (outer cover) needs to go in the hole with the plastic ferrule correctly too.......

 

that whole thread is good reading, although if i remember correctly it wasn't really completed with the detail the rest of it has.....

[Martin 2,130]

you might be able to hold the balls with a small amount of grease, but i just found it easier to have that area horizontal to keep everything in place while assembling.

[Jake217 20]

I studied the pic in the Onan manual noting the pin depth spec's. Not a great picture, but I think I've got it.  The more I think about it, I'm better off pulling the engine; just hate routing the wiring back in place on that thing, my C 's are so easy.  I'm going to do some research and see if the P224 cup is the same as the P220. If so, I might pick up a P224 camshaft gear on eBay cheap and see if I find a keyed, steel spacer in there.  Did you use Loctite on the non-keyed spacer?  If so, did you use blue, red, or something else?

 

I'm going to tackle this thing tomorrow. Thanks again for the help, Martin. Very much appreciated.

[Martin 2,130]

I would make sure that is your problem before buying any parts. I'm also not sure if all p224 engines had that keyed spacer, I think it's much the same as the smaller engines, some had them, some not.......The parts are interchangeable, I rebuilt my stripped timing gear p224 engine with p216 parts. I wouldn't use loctite myself......

Sent from my iPhone using Tapatalk

[Jake217 20]

Update.... Once I got inside, as expected, the spider gear popped off with relatively little effort.  The spider looks fine, no cracks, just a little stretched.  Instead of purchasing a new or used cam gear with a better spider, I decided to Loctite Blue the old spider on.  If it does not work, I will have to get a new cam gear anyway to get a better spider, so I'll just replace the whole cam gear along with the crank gear if I have to go back in.  The spider does not move now; not at all.  Also, I did the job with the engine on the tractor.  Surprisingly easy job over all. I used wheel bearing grease to hold the three bottom steel balls in place.  Checked their position in the cup with a flashlight to be sure.  The rest of the governor parts look real good and the governor pin is right on spec.

 

I'm just waiting for a new gear cover seal and gear cover gasket from onanparts and I'll button it up.  Thanks again, Martin.  I'm pretty confident this will fix things the rpm spikes..