Only Cub Cadets - Kohler M18 skip

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Only Cub Cadets (https://www.onlycubcadets.net/forum/index.php)

- Kohler Engines (https://www.onlycubcadets.net/forum/forumdisplay.php?f=50)

- - Kohler M18 skip (https://www.onlycubcadets.net/forum/showthread.php?t=50889)

olds45512

12-18-2017 11:55 PM

Quote:

Originally Posted by J-Mech (Post 441319)

Stan stated in the first post that he adjusted the carb rich to lean and can get a change in the engine. A fixed jet carb doesn't have any adjustment, so it is a safe assumption that he has an adjustable jet carb. Doesn't sound like a fuel issue to me.

Swapping plug wires doesn't help diagnose the issue.... he already stated that pulling the wires one at a time yields no change. The problem is across both cylinders.

Yes, this is a wasted spark engine, so both plugs fire at the same time.

I know the "swirl" plate you are talking about Beth. Some engines have them, some don't. I'm sure they are still available, but I don't know the number. I honestly don't know if they help much or not.

Stan,
A failing coil is possible.

Simple test:
Hook up a timing light and point it at the open hood. Watch the flashes and see if you have a misfire. Check both wires. If you do, plan on replacing the coil. If you don't, I'd go checking to see if you have a sheared flywheel key. No, it isn't likely, but who knows if the flywheel has been removed before and was correctly tightened on install. I'd also check the magnet to make sure it is still intact. (Ignition trigger magnet.)

Use the timing light and see what you find.....

Good to have you back Jon!:beerchug:

J-Mech

12-18-2017 11:57 PM

Quote:

Originally Posted by olds45512 (Post 441324)

Good to have you back Jon!:beerchug:

The needs of the many, outweigh the needs of the few. Or the one. :beerchug:

DieselDoctor

12-19-2017 12:31 AM

Thanks Jon. Welcome home.
I'll check with a timing light tomorrow. I had't thought of a sheared flywheel key, but that's exactly what it sounds like. Timing. Hopefully I'll have something to report tomorrow night. Stay tuned.

ol'George

12-19-2017 08:18 AM

Glad yer back Jon, ---you cantankerous young whipper snapper :biggrin2:
Do those mag coils have a built in electronic advance like some do?
I have not tried checking with a timing light, but the trigger "pellet" just don't seem large enough to contain the electronic's needed.:bigthink:

CubDieselFan

12-19-2017 09:34 AM

Sorry to hijack your thread Stan, welcome back Jon.

J-Mech

12-19-2017 09:51 AM

Quote:

Originally Posted by olds45512 (Post 441324)

Good to have you back Jon!:beerchug:

Quote:

Originally Posted by DieselDoctor (Post 441330)

Thanks Jon. Welcome home.

Quote:

Originally Posted by CubDieselFan (Post 441345)

Sorry to hijack your thread Stan, welcome back Jon.

Quote:

Originally Posted by ol'George (Post 441337)

Thanks guys. :beerchug:

No George. The Mag coils do not have an advance in them. :ThumbsUp:

DieselDoctor

12-19-2017 09:22 PM

Well, I dug out my old inductive pick-up timing light and didn't really see any distinct pattern in the flash that it was skipping on either cylinder. If I had to describe the sound of the skip in writing, it would be run run run run run PAH run run run run etc. Just every so often it drops a cylinder once and then fires correctly, but as I said previously it sounds like it is laboring. I pulled the motor to inspect the coil and flywheel key. The flywheel key is ok, the flywheel is tight, the magnets are tight and in place. The kill wire to the coil is fine. No noticeable burn marks or cracks in the coil itself. The air gap measures around 10 thousandths. Since I'm this far into it, I'm going to throw a coil on it. If I had one to test with I'd try that first but none in stock here in the shop. Who knows what little gremlins might live in the old coil. Other than throwing a coil on it, I'm tapped out. Are all the flywheels the same for the Magnums? I have no history so it may have been changed at one time. Any guesses?

J-Mech

12-19-2017 10:28 PM

Mags all use the same flywheel.

If you don't see it missing with the timing light, it probably isn't, but that doesn't mean the spark isn't weak. Or that the plug wires are good. They aren't replaceable, (which I hate, but hey, they didn't ask me how to make it) so it could even have a wire that has high impedance. Oh.... what brand spark plugs did you use?

You have no history of this engine..... Hows the muffler? Could be plugged up.

I suggest running it while it is about of the tractor. Could be something in the rear end causing it to labor. Again, not likely, but possible.

There are still several other things that I can think of..... but I don't want to send you on a goose chase as I'm just guessing. Stan, could you record a video of it running and link it up for me to hear it?

DieselDoctor

12-19-2017 11:08 PM

Next time I have it assembled enough to run it, I'll make a recording of it. I may need some help posting the recording though. I hope to have the new coil on Thursday. The new spark plugs are Autolites. What ever is occurring is happening on both sides I think. I have changed plugs around from one tractor to another as well. There doesn't seem to be a weak and a strong cylinder.

jaynjeep

12-19-2017 11:49 PM

Quote:

Originally Posted by DieselDoctor (Post 441401)

I had a single cylinder command a while back that had similar issues with intermittent missing... it turned out to be a weak coil... I hope this works out the same for you... sounds like you have eliminated most of the other possibilities.. keep us posted!!:beerchug:

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