Kohler K241

My K241 is about 40 years old +/- a few, and is on a Lincoln Weldanpower 150. Recently the engine has begun to miss during WOT operation. I'm certain it's not sticking valve(s). I rebuilt the carb, no change, and replaced points, condenser and spark plug. That helped out a lot with start up. Fuel pump maintains 3 psi at any rpm missing or not. Pretty basic engine, but the miss has me stumped, and its not a light miss, but rather catastrophic in nature. This miss only occurs once the engine reaches normal operating temperature. Once this miss begins, I can't get the engine above 2000 rpm without it missing. I finally put a spark plug ignition tester on it. Once the miss begins, spark is intermittent from bright to very dim in the tester. At this point, it's my belief there is a problem with the magneto or wires, which is/are beneath or under the flywheel. I suspect a bad wire which may be broken allowing the miss to happen once it begins to near normal operating temperature. I have yet to check for a bad/broken wire yet. Any other suggestions that anyone can give me would be welcomed. Rather anyone responds or not, I will continue to work through this issue until solved and will post my results once finished. As simple as this engine is, it's being a pain. One last question, is there an air gap setting for the magneto under the flywheel? I suspect it could be a fix setting and not adjustable. I cannot find a spec or setting for this in my service manual. Also, the ends of the magneto and the magnets are free of rust. Thanks for any information anyone sends my way.

Check your valve adjustment

Sounds like your ignition coil might be breaking down. A bad coil will show up at higher RPM's and under a load. If you have a shop that has a coil tester near you, might be a good idea to have it tested.

This manual may be of some help.

http://www.mymowerparts.com/pdf/Koh...al-K91-K141-K161-K181-K241-K301-K321-K341.pdf

You state "coil," but to make we are on the same page, my K241 only has a magneto (which also has a coil attached), not a separate coil mounted outside the engine housing. I will try to find out if there is a small engine shop around here which can test the magneto. I will also check the valve stem clearance too. I'm leaning towards the magneto too, but a check is cheaper. There are a few small engine shops around here and I do know one is a Kohler dealer. I have purchased parts from them, but all the data related to my K241 is on microfiche files, not on their computers. As for the shop manual, I have a copy that I printed out, but thanks for the web address. So far the manual hasn't helped much to locate the cause of the problem. I removed the flywheel today to get a better view of the magneto. It has four wires coming off it, spark plug wire, the wire which goes to the points and two wires which go to the welder/generator. This welder/generator has had intermittent issues with exciting the generator for power over many, many years. Problem was or is, it won't stay down long enough to find the problem, but as of the last 3 or 4 starts, no power output at all, again I believe the problem to be with the magneto not sending power to excite its field. Thanks again for the suggestions. As stated before I'll let you know what I find.

You might also have a problem with what I believe is a relay switch that the wire from your magneto attaches inside the welder unit. The relay apparently allows the high voltage circuit to turn on when the welder is running. But I'm recalling from memory from 30+ years ago and I might be wrong. The reason I suggested checking out the ignition coil on your magneto is that with 40+ years of age, the ignition coil is probably on borrowed time. Sometimes the coil will get kinda mushy when they start going bad and short out. Good luck!

I think that there is a relay just inside the housing of the welder. I didn't think too much about it until your mentioning it now. Two of the wires which run from the magneto go to this unit and if memory serves me right, there two other wires leaving it. I didn't see where these wires went to at the time, but will have to open up the welders housing again once I get the engine running properly. The welder/generator has acted up off and on over the past 40 +/- years. When the welder acts up, you can see a slight electric spark but it won't strike an arc. I also found that if I revved this engine up just a little, the welder/generator would excite it field and once allowed to return to normal WOT, the welder/generator would work normally as it should. Sometimes this problem would repeat itself each time I would start from a cold start and sometimes it would work correctly right from the start. Right now, the welder Isn't even giving me that slight spark when trying to strike an arc and may not be getting any electrical feed from the magneto. It could be that relay you mentioned. I'm on the wrong computer right now, but a Kohler Weldanpower owners manual which shows wiring diagrams on various versions of this welder/generator. But, my first priority is the get the engine to run properly. My gut leans toward the magneto as being the primary fault with the engine. I called a local small engine repair shop today. They said they would prefer to test the magneto on the engine, but I could just bring them the magneto to them and they could check just the resistance. I also found out that there is no air gap setting on this magneto, that it sits in a fixed position and is not adjustable. I read a post on anther forum where one individual said "you would need a cut away flywheel to adjust the air gap." I'm glad to see that isn't true, at least for my K241 Kohler.

Well I'm back without success in correcting my miss with my K241. I installed a spark tester. The spark tester shows that there is a problem in the ignition system. So far I installed new points and condenser, spark plug, and today I put on a new magneto. Checked wires with an ohm meter incase there happened to be a broken wire giving me intermittent continuity. Didn't find any continuity issues. Also, no pinched wires either. Block has been degreased and cleaned (see Pics) to eliminate the possibility of a electrical short through the oil and dirt. I read where if the condenser fails, I should see a yellow spark across the breaker points. I'm not seeing much of a spark across the points and the spark is bluish white when the points open. When the engine misses, there is unburned fuel leaving the exhaust. No back fires through the exhaust and no blow back out through the carb, but a definite loss of spark the spark tester. What am I missing? Could I have a bad condenser? What about the push rod that opens the points. I'm using the existing push rod. It doesn't bind or hang up when I remove it and it's not sloppy feeling. It moves in and out smoothly, although I can't operate it as fast as the engine does. This a very basic engine and it's kicking my tail.

One other quick note, I even had the kill switch disconnected just in case it was causing some problem, no luck.

Sec56 said:

One other quick note, I even had the kill switch disconnected just in case it was causing some problem, no luck.

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Did you check your valve adjustment?