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Discussion Starter · #1 ·
Ok my 316 seems possesed. When starting out blowing this am it seemed to be at the correct wide open rpm. Then after 5 minutes it seemed to increase. The govenor seems a little touchy but not bad. Should I adjust the wot. Or just mothe throttle lever or ????
 

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cvcman,

I had the same symptoms with a 1990 318 - Onan P218G a couple years ago. No amount of adjustment would eliminate the "run away" condition. After a lot of web research, I found that my "run away" condition was not unique.

In order to fully diagnose and repair my problem, I removed the engine from the tractor. I removed all of the engine cooling shrouds. The flywheel, stator and timing cover were removed. Once the timing cover is removed, the cam shaft gear is visible. The fly-ball governor is underneath the governor cup, which is in the center of the camshaft gear. It consists of a spider gear and 5 steel balls - fly balls.

The operation of this type of governor works like this: when at idle the governor linkage will allow the carburetor throttle plate to open only a short amount. At this low speed the fly balls rotate around the center of the camshaft gear at a small or tight radius, which does not force the governor cup out much at all. The governor cup is in very close proximity to the governor arm fork. The governor arm is directly connected, through linkages, to the throttle plate. When the throttle on the dash is increased, the throttle plate of the carburetor is opened a considerable amount, increasing the fuel and air mixture. This increases the engine RPM. The increased RPM will rotate the camshaft at a faster speed. This increased speed will force the fly balls out from the center of the camshaft. The fly balls will now be rotating at the formed "dish" of the governor cup. At this point, the governor cup will be moving out, away from the camshaft, putting pressure on the governor arm fork. This modulating action of the cup and arm will result in small, opening and closing actions of the throttle plate, maintaining the desired RPM.

My problem was that the spider gear, which locates the five fly-balls, was cracked. With the spider gear cracked, the spider gear and fly balls would not rotate at the same speed as the camshaft. Because it was not rotating at the designed speed, the fly balls were not effected by the inertia to increase their operating radius, which would have the affect of decreasing the engine speed. Others with this "run away" condition have reported that once the engine reaches operating temperature, the spider gear would slip on the camshaft, having the same result as my cracked gear.

To repair my engine, I was able to locate a good used camshaft, with a matching crankshaft gear. Once the engine was re-assmbled and installed in the tractor, it ran like a top!

For your reference, a member of MTF has created an excellent post: How to rebuild your Onan engine. Read the entire 4 pages. For your issue, pay close attention to posts #53,56, 93, 95 and 98. In the linked post, MTF member Vadeere has developed a creative solution to prevent the spider gear from slipping on the camshaft.

The repair my seem intimidating, but it really is fairly straight forward. I was able to source most of the technical information from the web, but that was 2 years ago. This information may not be available today. If I can assist you with any technical documentation, let me know.

I hope this helps. Sorry for the long post - kind of got carried away.
Bill
 

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Discussion Starter · #3 ·
_//// so now I'm in the middle of winter and I need to pull the engine ??? Great. I shouldve kept my Cub Cadet ... This really blows
 

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Discussion Starter · #4 ·
before I blow up this thing a question; my engine speed is not decreasing when warm rather increasing...It is like you put the throttle at full open and its running fine for 5 minutes or so, then the engine goes up another few hundred rpms and stays there so i have to back off the throttle....
 

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Silly question, but have you played with your carb settings at all? I had a light surge in mine this summer and readjusting the carb helped.
 

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Discussion Starter · #6 ·
I dont like messing with carbs unless I know what im doing, again it runs fine its just after 5 minutes or so the rpms increase so you have to throttle it back to 3/4 or it seems too high. It just started doing this. The governor is working but it does seem a little touchy but I can live with that...
 

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Frame Swapped '88 322
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I had this problem in my 1987 318 with the P218G, when the engine warmed up enough while cutting grass it would just runaway after about 30 minutes, and this summer it started doing this. Around the end of August I pulled my motor and my Cam gear was perfect, so I had someone on WFM make be a nylon key which can with stand up to 4,000 degrees, to fit in the plastic gear, so now it will not rotate, hence overrev. That gave my Onan a whole new lease on life!!!! That is how I solved my problem. That is most likely your problem.
 

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Three of my friends
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If you want to sell it put me on THE
list and you can get your cub cadet.
 

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Discussion Starter · #9 ·
do I need to tear down to do the plastic gear thing ?? What if I run it this way and just back off the trottle ??
The tractor and deck is mint and so is the blower....will sell for 10k cash:praying:
 

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Frame Swapped '88 322
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I would be careful if you run it like that. But when blowing or running, you will see as the warmer the engine gets, the more it will overrev/ runaway. Just my $0.02
 

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Frame Swapped '88 322
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Well, I think we nailed the problem for you, mine did the same thing and I fixed it. Nice looking 316!!!
 

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Discussion Starter · #13 ·
so does it have to be torn down to get at it ?? If so how much would a shop charge to do it ??
Could I do it wthout pulling the entire engine ???:crybaby:
My feeling right now is I should have kept my Cub...I like the deere and it runs real nice other than this issue...
 

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Frame Swapped '88 322
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Well I had to do some major disassembly of my 318. I am sorry but, you do have to pull the engine, I pulled mine and it took 45 minutes. This was the first time I have pulled it, it was pretty straight forward. I didn't send mine to a shop, so I can't say how much it would cost.
 

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Three of my friends
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Probably cost more for a shop to fix than its worth,most the owners here do their own work,might be better off parting it out.I had a 316 with 50 deck,rebuilt b43,new paint.got 900 for it.
 

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Discussion Starter · #17 ·
WOW now its a parts machine !! This is way too nice and with 800 hrs and a mint deck and blower....I just dont know about tearing it down...I may use it and just throttle it back...I dont mow with it and never have just use the blower....
 

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Three of my friends
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These motors turn 3200 ? Rpm,if it run over that don't be concerned,if it runs too fast loosen the cable clamp on the left side of the engine tin and slow it down or throttle it back.
 

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Discussion Starter · #19 ·
ok check this out; my buddy knows a guy that is a supposed Onan expert, I called him today to see if he could do the job. he said 250.00 but then started asking me a bunch of questions..I told him I changed the oil last summer and then havent run it till now.
He asked what oil I used and I said 15w40 Havoline...He said " theres your problem, run 3 oz of Seafoam in it and drain and chg the oil and filter and use 5w30 Mobil 1" he said the oil I used gets too sticky and heavy when it gets hot and it interfers with the governor...so i decided it was worth a try, I ran it with the Seafoam and drained it and chgd the filter, 2 qts of 5w30 Mobil 1..It seems fine now, I ran it for half hour in my garage, blew my neighbors drive and ran it up and down the road and it seems normal,,,could this be
 

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Well that's a new one on me. I would have thought the governor cup was the issue on this. BTW that is certainly not a parts machine, very nice looking!
 
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