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PK.
PK., Small Engine Technician
Category: Small Engine
Satisfied Customers: 1038
Experience:  Retired Owner of a full service shop and national parts sales website.
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I have a 1970 wheel horse lawn tractor with a kohler k321 engine

Customer Question

I have a 1970 wheel horse lawn tractor with a kohler k321 engine that stops when it gets hot. I can start it right back up and run it for another 20 minutes and then it will stop again. It will start right back up without letting it set for awhile. I have replaced the coil, points, condenser, plug, solenold, both battery cables and some other wires, I also cleaned all the cooling fins.
I have run a wire from the positive on the battery to the positive on the coil and it will still stop. I have rebuilt the carburetor and I tried a different gas tank that was gravity fed and it will still stop. I can tell that the engine is going to stop because just before it stops the sound of the engine will change. Sometimes when I hear it is about to stop I can slow down the engine speed and then it will keep on running, I can then speed up and cut for another 15 minutes.

Today I used SeaFoam motor treatment to free carbon build up around valve guides and valves.

Can you help?
Submitted: 5 years ago.
Category: Small Engine
Expert:  Ranwell1 replied 5 years ago.

Unless you put the wrong coil on it. (What do I mean by wrong coil?) Sontimes people try to save money and buy a coil from an autoparts store and they are not caomatable. (They don have the correct resistor in the) I have no idea how to help. other than if your carburetor float is set just alittle bit too low it won't let quite as much fuel into the carb as the engine is burning. When the engine shuts off, even the small amout of time between it dying and you starting it again, will be enough time for the carburetor to fill back up.

 

That's all I can figure....over and above what you said you did.

 

Other than this, it may be time to take it to a professional.

 

Good luck.

 

Customer: replied 5 years ago.
I put a Kohler coil on my tractor and the float was set right . Any other idea?
Expert:  Ranwell1 replied 5 years ago.

I have no idea what else it could be. Except vapor lokc, but I would think that changing the gas tank might have helped to eleimiate that. I will send my vapor-lock answer just in case.

 

Just read all of my answer before you act.

 

1. Todays gasoline is not the same as it was just a few years ago. There have boon changes in gas formulas. DO NOT USE REGULAR 87 OCTANE GAS! Use a good quality, good brand 89 octane fuel. DO NOT USE CHEAP GAS.

 

2. One of the problems you seem to have is a phonomenon called "VAPOR Lock".

This is caused when fuel vaporizes in the fuel line and doesn't allow the proper amount of gas to get to the carburetor. This is usually caused bu the fuel ine getting too close to a heat source such as the muffler of the cylinder head or even sometimes the engine block. Also cheap fule of 87 octane fuels will cause this to happen more often. Check all the fuel lines and make sure that they are away from heat.

 

As mowers are operated, they tend to accumulate grass under the engine shoud. We call this a "Birds nest or mouse nest." These nests will keep the engine from cooling as they block the flow of air to the head and cylinder. Clean this grass out several times a year.

 

3. Another issue can be a fuel issue in the carburetor.

As engines sit or get older, fuel that is left in the carburetor can turn to gum and varnish and cause this and other problems.

Also, any gasoline that was left in a gas can for a period of more than 30 days must be discarded because it also has begun to turn to varnish.

More than 70% of all of our repairs in our lawn mower business are due to this same issue. You most likely have dirt, gum, varnish...etc in your carburetor plugging up the small passageways and jets in the carb. It Must be removed from the engine, cleaned very well, blown out with compressed air and reassembled using a NEW carburetor rebuild kit. ALWAYS clean the fuel tank and replace the fuel line when doing this repair or you may have to do it all over again. The inside of the fuel line disintegrates over time and these small pieces of rubber will plug up the carb too. Dirt and water from a dirty fuel tank will also plug up the carb. Find the Model, type and serial or code numbers off of the engine and take them to your local dealer to get the carb kit.

 

4. Make sure that you install a new Air Filter. DO NOT CLEAN AIR FILTERS always REPLACE. Replace air filters no less often than every 20 hrs of use. Plugged air filters will cause many problems.

 

There may be other things, but this should be enough for now.

 

Please click "ACCEPT" or I won't get paid.

 

 

Customer: replied 5 years ago.
I have already rebuilt the carburetor, used a new air cleaner, cleaned the cooling fins, and checked for vapor lock. I know I have a strange problem, but there must be a answer. Is it possible to ask some of the other experts?
Expert:  Ranwell1 replied 5 years ago.

You can ask anyone you wish. I doubt that anyone else will be as qualitied as I am, but you never know..Someone else might have an idea.

 

 

I will leave this queston open and invie any other expert to give an anwer.

 

If they have a better answer, then you may accept their answer, but if they don't have a better answer, I would appreciat an accept sonce I did give a lot of information and work.

 

 

As of now I give permission to any other expert who wants to answer this question

 

 

 

Expert:  PK. replied 5 years ago.
Have you had the head off yet? Thanks, PK.
Customer: replied 5 years ago.

I have not taken the head off yet, I used Sea Foam motor treatment to free carbon from the valve guides and valves.

Expert:  PK. replied 5 years ago.

SeaFoam does a good job, I use it every day, but it's not going to clean the chamber in one use, or even a dozen. Removing the head and cleaning the carbon is a normal maintenance item for all L-head engines and might help your situation. While you have the head off you will have a chance to examine the cylinder and check the concentricity, or roundness, of the cylinder. You can use either an old piston ring or snap gauges and a micrometer to do this.

 

Also, can you tell me what your spark plug looks like after running for a little while? Is it black, gray, brown, etc.? Thanks, PK.

Customer: replied 5 years ago.

My spark plug is a chalky black.

Expert:  PK. replied 5 years ago.

I'd pull the head at this point. Chalky black is probably from incomplete fuel burning in the chamber and might be from excess build-up of carbon. It could be from the carburetor being over rich as well, but you'll never get the carburetor right if there's a lot of carbon build up in the chamber so check that first. You can often get away with re-using the head gasket, but I'd go ahead and replace it.

 

Also, it may be beneficial to move up in heat range on the spark plug. You're going to need to replace it anyway so a little hotter one might help.

Expert:  PK. replied 5 years ago.

I'd pull the head at this point. Chalky black is probably from incomplete fuel burning in the chamber and might be from excess build-up of carbon. It could be from the carburetor being over rich as well, but you'll never get the carburetor right if there's a lot of carbon build up in the chamber so check that first. You can often get away with re-using the head gasket, but I'd go ahead and replace it.

 

Also, it may be beneficial to move up in heat range on the spark plug. You're going to need to replace it anyway so a little hotter one might help.

Customer: replied 5 years ago.

I said the plug was chalky black today, but in the last couple of days I have been adjusting the carburetor trying to get the engine to run right. I checked the plug two days ago and it was light gray in color, I think the chalky black is because I adjusted the carburetor rich and did not clean the plug.

 

I don't know what to think, I have had this tractor for 30 years and have never had the head cleaned. The Wheel Horse mechanic of 50 years I have been using tells me it is an electrical problem and not the head. I'm just lost

 

Expert:  PK. replied 5 years ago.

The Kohler manual calls for removing the head and cleaning the chamber every 500 hours. We recommend every 100 hours with the fuel we've had for the past ten years.

 

It is possible that it's an electrical problem, but you seem to have already been down that route. So what I would do is ensure that all other aspects of the engine are in good shape, then you can diagnose by elimination.

 

Which ignition system do you have?

Customer: replied 5 years ago.

I have a battery ignition system.

New Kohler coil, new points, new plug, new condenser, new high tension lead, new battery cables. Points set to .020. Champion H10 plug set to .035. I have checked and replaced many of the wires and contacts on the engine.

I was told that if I ran a wire from the positive on the battery to the positive on the coil that I would by pass all the other wiring on the engine. I tried that and the engine still stopped. I'm thinking the new Kohler coil I bought might be bad . Is there a way to check the coil?

Expert:  Ranwell1 replied 5 years ago.
Plug should be set at .030 not .035
Customer: replied 5 years ago.
I just checked the kohler service manual again and it shows Kohler engine K321 with battery ignition system uses plug H10 with gap .035. Am I reading it wrong? I know the gap can make a big difference.
Expert:  Ranwell1 replied 5 years ago.

It probably isn't going to make the kind of difference that you are having, but we have been setting them at .030" for 30years. The newer ones sometimes have a different gap. You have tried everything else, so what's to lose by trying it.

 

 

 

Expert:  PK. replied 5 years ago.

There's not a way to test the coil for an intermittent failure. You can try testing it once you think it fails but it's not very accurate.

 

With a test light check for continuity between the positive and negative posts, the light won't light if the primary winding is bad. Then do the same between either post and the High Tension lead, you should be able to get tiny sparks, but the light won't light.

 

This method really isn't very accurate and the accepted test is simply to use a known to be good coil.

 

I think there's one key thing that you said in your first post and that is that you can keep the engine running by cutting the throttle back. If the coil is breaking down, you can cut the throttle back all you want but it's not going to make a difference. Also, a coil will have to cool back down so that the break in the winding can become continuous again.

 

I have to tell you that I have several hundred engines come through my shop a year. We always start with diagnostics first. And the first part of diagnostics is to make sure all systems are in proper order before replacing parts. In your case, with an older engine, the first thing I would want to check is compression and the condition of the cylinder and the chamber. Thanks, PK.

 

 

Expert:  Ranwell1 replied 5 years ago.

There is apossibility that you have a valve seat that is loose. This could be causing some of the problem.

 

What do you think? PK

Expert:  PK. replied 5 years ago.
If it has inserts that may be something to look for. Pulling the head is an easy job on these engines so I definitely think that's worth doing.
PK., Small Engine Technician
Category: Small Engine
Satisfied Customers: 1038
Experience: Retired Owner of a full service shop and national parts sales website.
PK. and other Small Engine Specialists are ready to help you
Customer: replied 5 years ago.

I took my wheel horse to a Kohler mechanic and he found that the intake valve was sticking and the engine was full of carbon. I now have my tractor back and cut my grass,( It now runs great). I did not hit the accept button because if that did not fix my problem I would have more questions for you. I think you helped solve my problem and I will now hit the ACCEPT tab.

 

Thank you

Great

 

 

Expert:  Ranwell1 replied 5 years ago.
I'm glad that you found the problem..Thanks for the accept.
Customer: replied 5 years ago.
I have already hit the accept button, so is there an error somewhere in the program? I hit the button yesterday. A new window came up and confirmed I hit the accept button.
Expert:  Ranwell1 replied 5 years ago.
Yes. you have already accepted. and thanks. At least according to what is printed on this post. I haven't gotten my payment from the site yet , which is unusual, so they may be having trouble with the payment , or something. I have contacted them and they should let me know what is going on. Someone will let you know. Thanks you for your question and acceptance of the answer. I just noticed. You may have acceper the other experts answer...it that is the case, then that is why it doesn't show up on my list. That's ok if it is that way.

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Retired Owner of a full service shop and national parts sales website.