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Jim_M

I'm stumped!

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I have a 68 GT-14 with it's original Kohler 14 horse engine. It's a good old tractor, runs good, starts good, or so I thought.

A couple of weeks ago I was going to start it and move it to a different building, I cranked and cranked and couldn't get it to start. It popped out of the exhaust so loud a couple of times that I thought it was going to blow the muffler off. I ended up pushing it outside for a while so I could move some other things around. After sitting in the sun for a couple of hours, it started right up and ran fine.

I've tried it a few more times since then and learned that if it's less than 40 degrees it won't start, it will pop out of the exhaust and that's it. If it's above 40 it will fire up and run fine. It's not water in the fuel, I've checked that and added a little gas line anti freeze to the tank just to be safe. It seems to me that the exhaust valve must be hanging open a little for it to be popping out of the muffler like it does, seems like the gas is exploding in the muffler.

Any ideas??

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I think the popping is simply due to the automatic compression release.

You are using full choke? You might take off the air filter and check to make sure the choke plate closes all the way when the choke is on.

I would also have a look a the spark plug and check the gap on it (and replace it if in doubt).

Finally, I would check the points. If you have not done so in the past 100 hours or so I'd just go ahead and replaces the points and condenser.

Best of luck. Happy New Year.

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Are you sure you are not over choking it. Popping out the muffler would indicate it is getting too much fuel.

Do you get any smoke immediately after it fires up?

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The choke is working fine. It doesn't matter what position the choke is in if the temperature is below 40, believe me I tried everything from full choke to no choke. The sparkplug is new and gapped properly, the points are good. The tractor starts and runs fine above 40 degrees, won't start below 40 degrees. It takes about 5 minutes of cranking to get it to pop below 40 degrees,and then it's burning the fuel in the muffler, not in the cylinder, when it pops it doesn't even try to start.

Could this be a problem with the automatic compression release? The engine still has 30 weight oil in it, I don't use it in the winter. I may have had this problem the whole time I've owned the tractor but just never noticed it.

I may try putting a lighter weight oil in it just to see if it changes anything. My thinking is that 30 weight oil may be causing the compression release to hold the exhaust valve open, even when it tries to fire.

It's not really causing me any problem, I don't need to use the tractor in the winter, but now that I know I have a problem I would like to fix it.

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Jim if your confident the carb is okay...I'm going to lean towards the ignition system

Throw a new plug in "if you haven't already", double check the coil connections...also "& again if you have not done already" change out the points & condensor.

Do you have a spark checker to see how the spark looks when your turning it over?

Again those can be misleading since the spark reacts differant under compression.

I wouldn't think 30/W would hae that dramatic of an effect on an engine at 40 degrees...maybe closer to zero.

Good luck with debugging it & keep us posted.

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The carb is fine. I put the sparkplug in it from one of my other tractors that fires up no matter how cold it is, cleaned every wire connection, swapped the points, condensor and coil from my other GT-14 and it still does the same thing. I put all the suspect parts on the other GT-14 and it fires right up.

I have an old magnetic "stick on" block heater laying around, I stuck it on the side of the block right under the clutch for about 10 minutes and the darn thing started like it was 80 degrees outside. It really acts like the exhaust valve hangs open when it's colder than 40 degrees. I checked the compression when the engine was cold and it was about 16 psi. After the engine is warmed up it's 94 psi.

I've got the shop pretty warm now so I can't repeat the problem, it starts every time, but I'll bet tomorrow morning after the shop cools off, it won't start again without the block heater.

I've never seen anything like it. :D

Anybody in here from Florida want to buy a really nice GT-14? :P

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Make me an offer.....just remember even though it has a snowblade on it right now, you might not be able to plow snow with it. :D

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Dump in some marvel mystery oil, it can fix anything. :D Seriously it does sound like a valve sticking or something. But when it gets into mechanical problems thats what I have two brothers thjat are mechanics for. :P

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I've got the oil draining right now while everything is still warm. I'm going to dump some 10W30 Mobil 1 in it tomorrow and see what happens, just for the heck of it. I'm done for the night, this thing gave me a headache!

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Jim,

Try a few tests first. :D

1)Pull the plug and squirt some oil down into the cylinder and turn the engine over with out the plug in. then reinstall the plug and see if the engine starts. If the engine starts the compression is too low. Pull the head to see if the gasket is blown or carbon has built up in the combustion chamber. You may have to turn the engine over to lift up the valves to check the seats for carbon build up.

2)Put a spark checker on the spark plug wire and make sure the ignition is working in the cold weather, during cold weather it is posible for terminals to lose contact.

Bill in Richmond, VA

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I tried the compression test cold without oil first, then used a shot of oil, and got pretty much the same low reading, so that rules out rings. The compression is great once the engine has been started and as long as it's above 40 degrees.

The only electrical component in the ignition system that I haven't changed is the ignition switch. I may try that tomorrow.

I've been switching parts between 2 identical tractors and everything that won't work on the problem tractor works fine on the other one.

Ever heard of the automatic compression release causing a problem like this?

If lighter oil and swapping the ignition switch doesn't do it, I'll pick up a head gasket and try your other suggestions. I'm leaning more towards it being something to do with the exhaust valve, so I think you may be on the right track with that suggestion.

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Ok! I can't take it anymore, I'm going back out to the shop and I'm not going to bed tonight until I figure this thing out!

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Jim, just a thought have you switched coils yet? but your right it sounds like you have a valve hangin up. easy way to check is to knock the electode out of a spark plud and hook a air line up to the plug and pressuerize the cylinder and listen to the exhaust and then the intake.

good luck, Steve

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It's 5 til 1 in the morning, but I found the problem! It was a weak exhaust valve spring. I could just about compress it with my finger and thumb. It must have been stronger when warm ??? All I know is, I put a good used one in and it starts first time every time and has good compression when it's cold.

I think I'll take a shower, drink a beer and go to bed!

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I've got a big Ash tree to cut up across the road from me today. The ground's too soft to drive the truck over there, I just might use the GT-14 and the ATV trailer now that it starts again. :D

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Glad that it turned out to be something easy to find and repair, even better you had a spare spring! The cold probably shrunk the spring enough to hang up the valve, and when it warmed up, was enough to close it. In any event glad to hear you're back in business.

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Glad you got it fixed Jim. Hope you had at least 2 beers to celebrate that one! :D

Eldon.

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