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Discussion Starter · #1 ·
I have been having problems for some time with my JD 314. When I bought it a couple years ago, it smoked a bit and leaked a bit of hydrostatic fluid, but nothing terrible. Just kept the fluids under close surveillance....then it started to have overheating issues. Eventually it blew the head gasket (due to a warped head from the heat). I decided at this point, a rebuild would be a good idea.

I rebuilt the engine once (new points, condenser, bored up to .020, new rings,seals, shaved the head to removed warping, even got new main bearings)...
After the rebuild, everything ran fine for a few hours but overheating started up again. After only 20 hours of operation and poor performance, I decided to open the engine up and inspect. What I found was heat damage to the piston, indicated by metal erosion on the top edge facing the valve side. In addition, a bit of scoring on the walls along the valve side. So...I had it honed and got new rings. What do I do now?

I cant figure out what is causing the overheating.
1. The points are adjusted to the required .020
2. The fins and grass screen are all clean
3. The Walbro carburetor is likely running a bit on the rich side (not too lean). The carb is also new.
4. The spark-plug gap is set properly.

Any ideas. It's important to note that I don't start having overheat problems until about 35 minutes of operation.

Could my hydrostatic transmission be the root of the problem. It has been acting strange lately, leaking more frequently. Could it be putting a heavy load on the engine?
 

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MARK ,you didn,t say if you had for compression .do you know how much end gap you have on the rings ,,do you know how much clearance you have on the piston .how do you know its not to lean did you look at the plug ,after it started over heating ..David
 

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Discussion Starter · #4 ·
David, for compression I was getting 125 psi (not sure how the automatic compression release effects this).

I didn't measure the end-gap, but I did mic the inside of the the bore to check the piston/cylinder wall clearance. My clearance was .010". (The manual calls this "Thrust Face to Bore" clearance).

As far as the connecting rod\crankpin clearance goes, I had a machinist look at this for me when I was getting the head shaved, he was reading .0013 (after bolts are torqued).

With regards to the carburetor, I'm assuming its running rich because the plug has a pretty thick coating of black carbon on it. (It was clean before I started running it). I didn't check it immediately after the overheat though, it had been running for about 15 minutes when I checked it.
 

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Discussion Starter · #5 ·
David, what kind of temperature should I expect my head to be operating at under normal circumstances (say, near the spark plug). I've got an infrared heat sensor gun, I was thinking about getting a reading to see how hot this thing is getting.
 

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Discussion Starter · #7 ·
Roy, well now that's a possibility. I've got a Walbro...I believe it's the "adjustable type" main jet (how can you tell?). What exactly is the best way to adjust this carburetor? I've tried to find a good set of instructions, but I haven't much luck with the Kohler manual because it seems there has been some variation in the types of carbs used over the years.
 

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Mark. You turn the idle mixture screw at an idle, to obtain the highest rpm. Turn in and out until you get this.
Do the same for the high speed mixture screw with it running at about 7/8 throttle.
Go back and forth a few times to check both of them.
Roy
 

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Mark,

If i'm not mistaken, the lower screw is the high speed, The one nearest the mounting flange is the low speed and the upper is is your idle. I've got one on my 314 and can't get it to work worth a darn. Wonder if the Walbro is your problem. I'd try and find a 30 Kohler. I've got a 26 I'm going to rebuild and try it since the 30 I have is on my 16 HP. If that doesn't work, I'll keep trying to find a 30 at a reasonable price.

Bob
 

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Some carbs the high speed is on the bottom of the bowl, I believe everything K-Series Kohler on John Deeres the adjustment is on the top.
 

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Discussion Starter · #16 ·
Alright, that makes sense. So, in my case the high speed air/fuel mixture screw is the lower one, and the low speed A/F mixture screw is the one that's near the flange.

Assuming I get this thing dialed in perfectly and I still have overheating issues. Where should I go next? (Please see the list of things I've done already, above)
 

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Discussion Starter · #19 ·
Alright, I think I might have my problem figured out.
1. My ignition timing was firing at 20 degrees ATDC instead of BTDC (could be part of the problem).
2. Fuel mixture was really rich, I've leaned it down a bit.

I also installed a cylinder head temp gauge to help monitor this overheating issue in case it persists.
 
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