Kohler K141T Overheating

[tntatro 181]

Hello, I have a Wheel Horse 656 that I repowered with a 6-1/4hp Kohler K141T that was originally on a log splitter. I've been having an issue with it shutting down when it gets hot. It shuts completely off like the key was turned off, although this engine is a pull start. It will start back up and only run on low idle. It will start up and run normal when cooled down. I originally thought it was the ignition and replaced the coil and condenser with new OEM parts and it still does it. I don't believe it's the fuel either because it pumps fuel, has new fuel line, OEM filter and new shut off valve with the screen. I then took out the valves and cleaned them up and ran a 5/16" reamer down the valve guides thinking that the exhaust valve may be sticking when it gets hot. So far nothing I've tried has worked.

I'm curious if maybe I'm just working it too hard. The mower has a 35" cut and I mow a lot in top gear up inclines and it's been pretty hot out. The engine is within the wear limits internally, has plenty of power and doesn't smoke or knock. It's set to about 3,500rpm at full throttle with no load.

Any opinions or suggestions on what might be wrong or where to go from here?

Thanks, Tim

[peter lena 9,430]

@tntatro  think you very well could  be working it too hard, that 3 rd gear inclines / mowing is pretty rough , BTW are you cutting at highest setting ?  ever drop the carb bowl ?  could easily be loaded with carbuncle's  , ever clean tank ? also might try  checking over your related wiring , corrosion , ground fault ?  what are you using for oil ? hi zinc  rating  stands up to heat stress . others will join in  with views . think  the regular repetition of the problem is your  track, to cure , pete

[tntatro 181]

Thanks for the response. I do have the deck on the highest setting. The carburetor has been cleaned. I cleaned the tank but it did have a lot of rust in it. I had to really work at it to get the old gas and flakes out. The wiring is simple with it being a pull start. All the wiring is new and I sanded places where it grounds. The oil is SAE30 for heavy duty diesel. I don't know if that has high zinc. I'm starting to think I may be asking too much from it. I never mowed with a 6hp before. My main mower has an 8hp Kohler and a 42" deck and it seems to do well. I'd rather have a 36" on it but it's been holding up with the 42" for a couple years. I'll have to find some high zinc oil just to see if there is and change. The 656 does seem like it may have been meant for smaller lawns with the original 6hp Tecumseh. If I can't get it figured out then I may have to put a K181 on it. The strange thing is that the K141 and K181 blocks look the same and I believe have the same bore and stroke. Not sure what makes one 6hp and one 8hp.

[oliver2-44 10,964]

1 hour ago, tntatro said:

 I believe have the same bore and stroke. Not sure what makes one 6hp and one 8hp.

The K181 has a longer stroke

[953 nut 61,989]

10 hours ago, tntatro said:

The oil is SAE30 for heavy duty diesel. I don't know if that has high zinc.  That is a good oil with good zinc content.

 

13 hours ago, tntatro said:

I've been having an issue with it shutting down when it gets hot. It shuts completely off like the key was turned off, although this engine is a pull start. It will start back up and only run on low idle. It will start up and run normal when cooled down.

I would start by removing the engine tins to make sure the cooling fins are not clogged up preventing the engine from cooling properly.

If your fuel line is too close to the engine you could be developing vapor lock in the fuel line.

[tntatro 181]

9 hours ago, oliver2-44 said:

The K181 has a longer stroke

Okay, that makes sense. 

[tntatro 181]

I actually had the engine apart and pressure washed the block so the fins are clear and reasonably clean. I just looked at the fuel line and it doesn't touch the engine. It's got a good amount of distance from it. 

 

I'll try a different spark plug even though the one in it was new. I've been messing with this engine quite a lot since I got it and originally it would only run at low idle, even when cold. I thought it was the ignition and have actually tried four different coils and four different condensers. Three coils were new and two condensers were new. I finally got it to run on high idle when I closed the points down to around. 012" with the last ignition but it would die after mowing for 20 minutes or so and seemed to get worse each time I used it until I couldn't even do a lap around the yard. It would start and stay running at very low idle though. Then I put in new OEM condenser and coil with no change. That's when I reamed the valve guide and then I was able to mow for a half hour or so. I should have took measurements on the valve guide and stem. My reamer was tight running through the exhaust guide and I don't think it's very sharp and didn't cut any material. It just scraped out a small amount of carbon and oil. I think the points are set around. 014" to .016" now. I could close them closer to .012". It won't even start at .020" when I put the last coil and condenser in I just kept closing it until it would run at full throttle. 

[oliver2-44 10,964]

 

A K141 would be an early/mid 60's engine. I wonder if  the bore and rings are just  worn out. 

That engine doesn't have a compression release, so it would be a good idea to check the compression. 

if's its good, a leak down test could also tell you some things about the health of the engine.

Just thinking out loud.

[oliver2-44 10,964]

I forgot the bore is also smaller on the K141.

 

K141 2.875 x 2.500

K181 2.938 x 2.750

http://gardentractorpullingtips.com/engspecs.htm

[kpinnc 15,526]

If you haven't already done so, I would check the muffler too. A clogged up muffler can make it run hot and weak as well. 

 

A good carb clean and adjustment can also clear up issues. Just dump the bowl if nothing else. With the poor quality of today's gasoline, a little gunk can make for a mix that is too lean. 

Edited August 12, 2024 by kpinnc

[953 nut 61,989]

23 hours ago, tntatro said:

I think the points are set around. 014" to .016" now. I could close them closer to .012". It won't even start at .020" when I put the last coil and condenser in I just kept closing it until it would run at full throttle.

The ignition points gap adjusts your ignition timing. Your engine may have a spark advance camshaft that adjusts the timing depending on engine RPMs. It will retard the spark at very slow RPMs ( starting) and then advance it once the engine starts. Check the engine data plate to see what the Spec Number suffix is. If it is "C" or higher then you could use static timing, if it is "A" or "B" then a timing light will be required.

This link will take you to information on this site for the K-141 Kohler engine.   https://www.wheelhorseforum.com/search/?&q=K141&type=downloads_file&search_and_or=or&sortby=relevancy

 Here is some other information on battery ignition systems.

With a battery ignition system, the ignition points are closed the majority of the time. With the points closed and the ignition switch ON the primary windings o

Gapping the ignition points at .020 has always been the standard answer to how points should be set. That probably will get you into the ballpark where the engine will run, but with a bit of additional effort you can improve the engine’s power and performance.

The Kohler engine manual in the Red Square files section covers two methods for setting the ignition timing, Static Timing and using a Timing Light. This manual is a relatively new manual and it overlooks the fact that many of our engines were built prior to the ACR (automatic compression release) camshaft.

Earlier engines (mostly 1965 and earlier) had a Spark Advance camshaft that can not be timed using Static timing. At rest (and very low RPMs) the timing is retarded to fire slightly after TDC. The timing mark (SP) on your flywheel is at twenty degrees before top dead center but at rest the points on these engines break about ten degrees after top dead center. The only reliable way to check or set the timing on these engines is with a timing light.

There are a couple ways to determine what camshaft you have. Presuming the camshaft in your engine is the one it was born with the data plate on the engine has a suffix that can tell you what camshaft was used. The table below will tell you the suffix applicable to your engine. The other way to determine what camshaft you have is to remove the cam gear cover and take a look. If you see a mechanism attached to the cam gear it is the ACR cam.

 

 

The following engines have the spark advance camshaft;

K-141, Suffix prior to “C”

K-161, Suffix prior to “J”

K-181, Suffix prior to “D”

K-241, Suffix prior to “D”

f the ignition coil have current flowing through them and are developing a magnetic field in the iron core of the ignition coil. The moment the ignition points open the magnetic field collapses and induces a momentary high voltage pulse in the secondary windings of the coil which goes through the spark plug wire and arcs across the gap of the spark plug. If this occurs in the presence of a compressed fuel/air mixture of the proper ratio an explosion will occur within the cylinder. If this explosion occurs at the proper time in the engine’s cycle there will be pressure applied to the piston forcing it downward on the power stroke. The ignition points will continue to open further after this has occurred. How far they open is immaterial, their work has been done for that cycle of engine operation. What is important is when they open relative to the position of the piston on its compression/power revolution. If it occurs too soon there will be backfiring, too late and there will be a reduction of power. In the case of our Kohler engines the sweet spot is twenty degrees Before Top Dead Center, that is what the “SP” mark on the flywheel is set. At the moment the points open the condenser quenches the arc across the points extending their life, the rest of the time it just sits there.

Static timing can be done with Kohler engines that do not have a Spark Advance camshaft. The instructions in the Kohler Engine Service Manual for static timing of the later ACR camshaft engines calls for an Ohm Meter to be used. I prefer a 12 Volt Test Light. The light will be connected between the battery “+” terminal and the lead that connects the points to the coil (disconnected from the coil). When the points are closed the light will be on, the moment the points open the light will go off. You don’t have to be focused on it like you would on a meter. With the test light situated near the sight hole for the flywheel (spark plug out so the engine will turn with ease), turn the flywheel slowly by hand in the clockwise direction (counter-clockwise if on the PTO end) until the moment the light goes out. If the “SP” mark is centered in the hole you are done, if not you have a little work to do. If the points are opening too late, they need to be opened further, if it occurs too early they need to be closed up some. Make gradual adjustments until the “SP” mark on the flywheel is centered in the sight hole at the moment the light goes out. Now tighten the screw securely and turn the engine over several revolutions to be sure the points are consistently opening at the proper moment.

 

[tntatro 181]

22 hours ago, oliver2-44 said:

 

A K141 would be an early/mid 60's engine. I wonder if  the bore and rings are just  worn out. 

That engine doesn't have a compression release, so it would be a good idea to check the compression. 

if's its good, a leak down test could also tell you some things about the health of the engine.

Just thinking out loud.

The guy I got the engine from said it was from a log splitter he bought in 1984. He said the splitter got damaged so he took the engine off and it's been sitting ever since. I took the engine apart and the crankpin, bore and piston are all within the wear limits. even the ring end gap was within the limits. The exhaust valve was stuck but I was able to pry it out with a claw hammer without much effort. I only had to clean the guides and valves up and lap the valves. The engine appears to be in great shape internally.

[tntatro 181]

22 hours ago, oliver2-44 said:

I forgot the bore is also smaller on the K141.

 

K141 2.875 x 2.500

K181 2.938 x 2.750

http://gardentractorpullingtips.com/engspecs.htm

I think there were different bore sizes on the K141. Mine was 2.938. As far as the stroke, I think I confused the K181 specs with the K161. I believe the K141 and K161 use the same rod. I don't know if the stroke is the same. The repair manual I have shows the specs for the K91 up to K341 but doesn't have the K141 in it for some reason. This engine is a 6-1/4hp K141T.

[tntatro 181]

10 hours ago, kpinnc said:

If you haven't already done so, I would check the muffler too. A clogged up muffler can make it run hot and weak as well. 

 

A good carb clean and adjustment can also clear up issues. Just dump the bowl if nothing else. With the poor quality of today's gasoline, a little gunk can make for a mix that is too lean. 

This engine has one of them flat oval mufflers. I may just put a new muffler on because the one on it is pretty rusty and has some small holes in it. Thanks, I kind of overlooked that possibility.

As far as the carburetor, both the throttle and choke levers were froze up and I had to work at them a bit to get them free. I soaked it overnight then put it in an ultrasonic cleaner and then sprayed the holes with carburetor cleaner. I also had to replace the bowl and float. The engine usually starts with one pull and runs great with plenty of power. It just quits after a while with no signs leading up to it. It just shuts off.

[tntatro 181]

3 hours ago, 953 nut said:

Check the engine data plate to see what the Spec Number suffix is. If it is "C" or higher then you could use static timing, if it is "A" or "B" then a timing light will be required.

Thanks for all the information. The spec number is 29357d so according to that information I can do a static timing. The flywheel housing doesn't have a hole in it to see the timing marks. I did do a static timing on it once after replacing one of the coils (Maybe I should be calling them magnetos?) but the timing marks were different than on my other engines with battery ignition so I wasn't 100% confident I had it right. I tried figuring it out based on prior experience and I think the points were set closer to .012" than they were .020". Whatever I did, it still had issues. The points can't be set any lower than .012" or it will rip the starter rope out of my hand when I try to start it. Anything higher than .016" and it won't start. I do remember that the piece that the magneto slides onto is delaminating on one side. It's made from layers of metal and held together with pins. One of the pins must be worn out and the layers are separating in that area. I wonder if that could cause a problem.

At this point I think possible issues could maybe be

spark plug 
muffler 
delaminating magneto mount?
maybe a bent exhaust valve because it was stuck open when I got it and I had to pry it out

timing

Just getting worked too hard

 

It seems ignition related to me but I don't know. I think I'll replace the spark plug and muffler and try static timing again to see what I get. This is what I get for rescuing Wheel Horses. I buy it for $50 and then put way more money in it than I could ever sell it for. I guess I should have learned after the first five or six.