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JD 316 engine running funny


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#31 Leonard VanCamp OFFLINE  

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Posted December 02, 2017 - 08:56 PM

What is ‘egging on the cylinders’?

Means the cylinders are out-of-round, Onans will wear at the bottoms of the cylinders.


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#32 Dspangler OFFLINE  

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Posted December 02, 2017 - 08:59 PM

Means the cylinders are out-of-round, Onans will wear at the bottoms of the cylinders.


Ahh ok. Thanks for the tip!

#33 Dspangler OFFLINE  

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Posted January 13, 2018 - 04:32 PM

UPDATE: I bought a new carb for the 316 as the one that was on it was missing screws and I didn’t want to work on someone else’s failed attempt at maintenance. Once the carb was installed, along with intake and exhaust manifold gaskets, she fired right up and sounded strong. Will test her out tomorrow to see if the new carb makes a difference.
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#34 Dspangler OFFLINE  

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Posted January 14, 2018 - 10:38 AM

UPDATE to my previous update: went out to plow, and now when the hydro lever is pushed past half the engine dies.. still runs a little rough too. Could I be looking at valve issues again? I noticed once that it back fired when I tried to go full on the hydro. Thoughts guys?

#35 secondtry ONLINE  

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Posted January 15, 2018 - 12:00 PM

 Ok I went back through and re read the thread. Trying to get a handle on your problem. Noting the low compression is most likely the result of excessive wear of the cylinders, rings or both. For diagnostic purposes it doesn't make much difference which. If the engine is worn enough to lose that much compression then there is almost certainly significant wear in other parts of the engine. The fact that the compression is fairly even between the cylinders indicates that it is caused by more or less normal wear. A burnt valve or stuck ring only effects the cylinder it is in as far as compression goes. I believe from what you have said your engine is due for rebuild/replacement. You could try just replacing rings but if you take it that far apart it would make no sense not to inspect and repair the rest of the engine.   I have not rebuilt an Onan engine myself. Parts are extremely expensive.  Re-power with a less expensive engine is a possible solution but not a particularly desirable one. Don 


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#36 Dspangler OFFLINE  

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Posted January 15, 2018 - 01:38 PM

Ok I went back through and re read the thread. Trying to get a handle on your problem. Noting the low compression is most likely the result of excessive wear of the cylinders, rings or both. For diagnostic purposes it doesn't make much difference which. If the engine is worn enough to lose that much compression then there is almost certainly significant wear in other parts of the engine. The fact that the compression is fairly even between the cylinders indicates that it is caused by more or less normal wear. A burnt valve or stuck ring only effects the cylinder it is in as far as compression goes. I believe from what you have said your engine is due for rebuild/replacement. You could try just replacing rings but if you take it that far apart it would make no sense not to inspect and repair the rest of the engine. I have not rebuilt an Onan engine myself. Parts are extremely expensive. Re-power with a less expensive engine is a possible solution but not a particularly desirable one. Don


Thanks for your input Don. At this point, I have to determine if i want to devote that much time and money into it, or unload it in hopes of finding another comparable machine. I hate to just get rid of it, but I don’t have the means and knowledge to rebuild it right now.

#37 coxhaus OFFLINE  

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Posted January 15, 2018 - 01:43 PM

Try running some seafoam in the gas.  It may clean some of the carbon out which can be good or bad.  It is a cheap try.


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#38 Dspangler OFFLINE  

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Posted January 15, 2018 - 03:02 PM

Try running some seafoam in the gas. It may clean some of the carbon out which can be good or bad. It is a cheap try.


Thanks! That’s the first thing I did with it however when I brought it home a few months ago.

#39 Dspangler OFFLINE  

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Posted May 20, 2018 - 09:57 PM

UPDATE: I finally decided to nut up and start to tear into the 316. I’ve included some pictures of my findings. I noticed quite a bit of carbon build up on both heads. I also found a puddle of oil in one of the valve boxes. The other box had some oil in it, but not nearly as bad. Could this be a valve issue? I’ve heard from others that the way it’s currently running, it most likely needs a rebuild. While I don’t have $1,300 for a rebuild kit right now, I’m attempting to do the small stuff to try to buy some extra time. This isn’t a serious worker. Just some summer joy rides and snow plowing in the winter. The plugs also have some pretty good carbon build up on them also. Also, has anyone ever tried using some compression restore liquid in the oil?

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#40 KennyP OFFLINE  

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Posted May 21, 2018 - 05:00 AM

As far as the oil in the valve boxes, make sure the drain hole is open in the bottom. That could be from many things (worn rings, loose valve guides, plugged crankcase vent). if you are going to rebuild it just now, You could try the compression restore stuff. I would add some MMO to the oil and gas to help clean any carbon that may be at the ring grooves.


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#41 Dspangler OFFLINE  

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Posted May 21, 2018 - 08:22 AM

As far as the oil in the valve boxes, make sure the drain hole is open in the bottom. That could be from many things (worn rings, loose valve guides, plugged crankcase vent). if you are going to rebuild it just now, You could try the compression restore stuff. I would add some MMO to the oil and gas to help clean any carbon that may be at the ring grooves.


MMO? Are you talking like seafoam? Or is there an actual product called MMO?
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#42 toomanytoys84 OFFLINE  

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Posted May 21, 2018 - 02:11 PM

MMO? Are you talking like seafoam? Or is there an actual product called MMO?


Marvel mystery oil
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#43 Dspangler OFFLINE  

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Posted Yesterday, 09:32 PM

UPDATE: I adjusted the valves tonight. They were all super tight with no clearance when at full rest. I adjusted to .005 for intake and .013 for exhaust. Next will be cleaning the heads and the tops of the cylinders and the valve heads of all the built up carbon. Then reassemble and hope she fires off.. the firing part probably won’t be til this weekend unfortunately. Stay tuned!




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