Kohler k301 runs rich, quits under load
 

Hi all,
I got a Cub Cadet 1200 last fall that I've been using for snow plowing & hoping to use for mowing in the spring.

The problem is when under heavy load it tends to stall or quit. It occurs after running about 10 minutes and especially when in high gear pushing snow. The engine will go from sounding strong to muffled and slow.

At that point if I don't play with the throttle and put it in neutral it will usually die. Sometimes it will backfire and/or spit a lot of black smoke out the exhaust. Every time I pull the plug it is black & oily. Once this happens once it tends to happen over & over again until I let it sit a while.

So far I have:
Replaced points & condenser
Installed a new carburetor
Tried multiple spark plugs
Checked the spark (strong & blue)
Changed oil
Checked all the wiring
Messed with the carb adjustment screws more times than I care to
Added mystery oil to the gas

I've learned a lot about these engines but it's starting to get a bit frustrating. Not sure what to do next. Any suggestions?

Did it do this before all the new parts? Did you check fuel flow from the tank? Do you have a fuel filter on it? Could be a fuel problem, I wonder if it ain't carbon build up on the head hitting the valves? I'd check fuel flow first then double check your adjustments on the carb. If no ones ever been in that engine I'd say it's carbon build up. Once it gets hot it's putting the Valves in a bind. I'm sure Jon and Don have better advice, they should be along to comment soon.

Have you considered carburetor icing as a possibility?

:Welcome2:

Wow, you replaced a lot of parts! Hope you saved the old carb.

It's a sticking exhaust valve.

Need to pull the head, take the valves out, de-carbon everything, plane the head, clean the valves and guides, and put it back together. Valve job would be in order too if it was my machine.

If you question my diagnosis, you can confirm by getting it to act up, then taking it inside, pulling the plug and using a blow gun (with a rubber tip) on an air compressor to put a little pressure in the cylinder through the plug hole. You should hear air coming out the exhaust even if you roll the motor.

Note: DO NOT roll the engine by hand while putting air pressure in the cylinder. It may turn on it's own, and hurt you. Stop the air to roll the engine.

With my limited cub time I have not had the valve issue yet. I have had the coil thing and this sounds like it could be that too. I know you said it has good spark but that is always a little iffy grounding a plug and looking at it. I am sure it needs a carbon clean either way so pulling the head is never a bad move. I like the run it till it acts up and put the air too it. If no leaks start it right back up and see if it still act up. Don't rule out a coil if it passes air test. I would sure do some more dio before throwing any more parts at it. J-Mech has forgot more about these things than I will ever know so a good air test is in your future.

If plug is oil soaked it could be rings, or valve seals.

Really? I think that's a pretty good test. :bigthink:
If he is getting a nice blue spark..... I think we can rule out that the plug isn't getting grounded good. Plus, if the coil was failing, I doubt he would get a nice spark even when the coil was cold.


Oil on the plug can also be caused by low compression due to a stuck valve.
K series Kohlers don't have valve seals. :bash2:

[QUOTE=J-Mech;315810]Really? I think that's a pretty good test. :bigthink:
If he is getting a nice blue spark..... I think we can rule out that the plug isn't getting grounded good. Plus, if the coil was failing, I doubt he would get a nice spark even when the coil was cold.


This could very well be true, you have worked on more of these than I will ever see. I do know sometimes you can get a spark when the plug is pulled but under compression it won't jump. A nice blue spark could but a good spark to some is not much to others. I know I chased a coil for a while and run for a while, run like crap, idle but not throttle up, come back for a minute and then fall off, die and restart after a few minutes and run fine are all signs I had. I chased fuel for a long time since every time I pulled bowl it would have a little rust in it so I just kept thinking fuel. I was lucky the motor was good since a coil is real easy to fix. Not that pulling a head is hard, just takes longer than bolting on a coil. Coils aren't cheap so I would test before throwing stuff at it and see what sticks.

Compression has no effect on spark.

Here's a link to everything anyone might want to know about the theory of spark plug discharge and the factors affecting the voltage needed to obtain a discharge.

http://naca.central.cranfield.ac.uk/...report-202.pdf

I kinda agree with red211

#2 A defective ignition system will cause an engine to crank over but not start. This could be due to no spark getting to the spark plug, a spark that is too weak to sufficiently burn the compressed air/fuel, or a spark that occurs at the wrong time.

An easy way to check for no spark, or weak spark, is with a spark tester that forces the spark to jump a large gap. This device may look like a spark plug but it is designed to demand a firing voltage of at least 20 KV. Another style has an adjustable air gap. Be sure to open this air gap far enough to force the ignition coil to put out over 20 KV. This is important because a weak ignition coil can easily generate enough voltage to jump a normal spark plug gap outside of the cylinder at atmospheric pressure. Inside the cylinder, where you can not see, the spark must jump the gap under compression pressure and this requires more voltage. A spark plug that fires outside of the cylinder may fail to spark when it is installed in the cylinder head.

from this link
http://www.linnbenton.edu/auto/perform/no_start.html

I have been studying the two articles mentioned. They seem to disagree, near as I can tell. There does appear to be a need for somewhat higher voltage to jump a gap at a higher compression ratio. HOWEVER, as the engine warms up and spark plug electrode temperature changes, that greater need is reduced as a hot electrode has a greater ability to carry an electrical charge. In other words, it takes less voltage that hotter the plug gets. It appears to be enough greater to overcome the added need for voltage due to the higher pressure. I want to note, that this lab test was on a stock engine. We are not talking about high performance...... so no need to go there. The above linked scientific study was done on a regular engine, and that's what we're working on here.

Listen guys..... there are two different approaches to internal combustion engines. Theory, and practical application. I delve into theory whenever I can because I find it intriguing. However, it seems, that my experience and practical application win out every time. Yes, I do concede that it takes more voltage to jump the gap at a higher compression ratio, but... from the first article it would appear that the difference is minimal. (On a stock motor.) Perhaps as high as 1000 volts, which in 10K volts, is pretty minimal. Besides, once the plug warms up it seems that it overcomes that need. If we wanted to dig into high performance, I know that with a "custom built", or performance, motor, with a significant increase in combustion pressure, there is a need for higher voltage spark. There are several other factors that play into this need outside of an increase in pressure, but I'm not getting into them in the interest of it's really irrelevant for the conversation.

My point: in this case, there isn't enough of a higher voltage required to say that if the plug fires well outside of the engine, that it won't when installed.
So, I'm going to quantify my post #9 by adding the words "in this application". I do agree with ironman on his recommendation of using a spark tester with an adjustable gap. It is the most simple way to visually see if the coil is weak. However, a simple OHM check of the coil while it's hot would also verify whether it is failing.

I'm sticking with my sticking exhaust valve diagnosis anyway.

I got the same thing as you from the article, which was it would only take a small increase in voltage to make up for the increased compression, with the gap being the biggest factor. However, "Automotive Technician Training: Theory" By Tom Denton claims that you need 4-5 kV to jump a 1mm gap under normal atmospheric conditions , but 10kV to jump the same gap inside a cylinder at 8:1 compression. So double. I've come to rely on the popular practice of pulling the spark plug out, and if I see a spark I'm good to go on electrical - look elsewhere. But if this information is correct, it may be useless except in the case where there is no spark at all. Very intriguing.

Thanks for all the info. This forum is great! You guys are operating on a different level than I am but it's great to know a bit of the theory behind these things.

I've never taken an engine head off before. What am I looking at in terms of time/skills/tools required? I'm researching on google but thought I'd ask.

I don't have an air compressor/gun, I'll have to see if I can get access to one for the test.

I bought the 1200 after moving in December to a 2.5 acre property with a narrow, 800 foot driveway. When it ran well, the 1200 was in a lot of ways more effective than my hired plow guy - he let the snowbanks get too narrow for him to manuever with all the New England snow this year.

I have a 44 inch mower deck that needs a belt and some rehab, and assuming I can get the engine going I'll be looking for a snowblower attachement in the fall.

Taking the head off requires no special tools,just something to remove the head bolts, but you will need a torque wrench and a head gasket to put it back together. As far as time and skill, not very much of either. Use a piece of cardboard, make some holes in it with a screwdriver and stick the bolts in it in the approximate shape they were bolted in. This way they can go back in the same hole. Don't remember if they're all the same on the K series, but on the Magnum I think the two center ones are different lengths, so it pays to keep them organized.

Link to the tech library.

http://www.onlycubcadets.net/forum/f...splay.php?f=19

You'll find the manual for your tractor, the engine in your tractor, how to resurface the head and lot's of other useful info.

Thanks for the tip.

Exactly what I was looking for! I've spent a ton of time searching for instructions on these engines yet somehow hadn't come across this yet. Thanks!


Answering some earlier questions - flow through fuel line is good, no fuel filter but I plan to add one, there is some sediment visible at the bottom of the tank so I will need to clean that out too.

Like you I had never opened up and engine before last summer. I pulled the head and valves on my 1450 and cleaned everything up. It fixed the sticking valve problem I was having. Like mentioned you will need a torque wrench and I would suggest a valve spring compressor; I used two screwdrivers on the valves.....never again. The manual has all the torque specs and tightening sequence. If you can use tools, you can do it. :beerchug:
Here is my thread.

http://www.onlycubcadets.net/forum/s...ad.php?t=32948

Bill

Just to beat the dead horse :beatdeadhorse: on the plug spark. I check for spark the same way, pull plug and watch for arc. This method has always worked when checking. In auto mechanics class they went through the compression/resistance thing and that was why I mentioned it. My reasoning was when the bad coil I had would mess up the engine would run, although weak and crappy. Checking spark like that would have told me nothing at that stage since it was still running, kind of. A quick coil ohm should have showed the failure but at that time I didn't know the spec.
Did you check for spark when engine was dead or after it was running again? That question sounds kind of stupid but it could apply. I would still go with the valve, coil is just an easy check if done at the right time.
Dang you guys are some smart cookies!! :beerchug:

Hi All,
I got back to this today after a hiatus. I pulled the head; low and behold there was a good bit of gunk:

Attachment 63292

I cleaned as much as a could using a plastic scraper, brass wire brush, wide flat screwdriver, paper towels, shop vac, and mystery oil:

Attachment 63293 Attachment 63294

Attachment 63295

Next steps are to clean it up a bit more, pull the valves and clean them, put it back together and see how it works.

A couple questions:
- The head gasket appears to be in good shape, should I get a new one or could it be re-used?
- The area around the engine block is filled with some sort of insulation-type material. You can see it at the top of the first picture. What is this and is it supposed to be there?

by the looks of it id say that gasket wasn't sealing properly, either why you'll need a new one. the head is probably warped and will need straightened.

The head gasket is blown/leaking. I can see it from the pic. No, you cannot reuse them. EVER.

See post #4 to read my recommendation again.

Just to reiterate a point: Plane the head.


NO. Get that all cleaned out. That is making the engine overheat..... which is what more than likely caused all this trouble.

Ok thanks. Just to clarify, plane the head means this, correct?:
http://www.onlycubcadets.net/forum/s...ad.php?t=22831

Yep, sure does! :ThumbsUp:

While you are this far into it, if you have time, you may as well pull the engine, do a general cleanup, inspect the ISO mounts and repair/replace as needed, check and tighten engine to cradle bolts, remove the flywheel tin and clean, etc, etc, etc....You will more than likely find the shroud and flywheel full of grass, mouse nests and who knows whatall adding to the overheat problem. You can also resurface the head yourself using a flat piece of thick glass and sandpaper. It will probably cost $20 and up to have a machine shop do it.

Do it all right the first time and you will be rewarded w/years of service. The 1200 is a great little tractor and I use the heck out of mine all year. It's my favorite plow rig.

BTW Kohler recommends doing the head carbon removal thing every 500 hours.

Update: ordered an OEM gasket. Will be out of town this weekend so may not get to the valves until the weekend after.

I did the ISO mounts when I first got it. The PO had replaced the drive plate and bushing, which were destroyed prob due to the mounts being bad, so that was my first taste of working on the 1200.

It still needs a new flex coupling down on the other end; I have one but when trying to install could not get the old one out - the driveshaft would not budge. I loosened the cradle bolts on the engine but still no movement. I had already tightened the adjusting nut on the clutch which had helped make shifting gears far less violent than before, so eventually I gave up and bolthed the old flex disc and couplers back together... Maybe I'll try again now that everything is apart. Am I supposed to knock out the pin on the coupler to do this job? Or is it a matter of moving the whole engine+driveshaft? do I need to disconnect/disassemble the clutch somehow?

Not sure I'll pull off the flywheel tin, from what I can see it looks reasonably clean and I've got to stop somewhere. Thanks for the suggestion though.

Thanks, I hope that will be the case!

That insulation gunk is debris from mice, grass (?), dandelions, etc. that affects the cooling of your engine. Clean it out and look for that at periodically as part of a preventative maintenance plan -- it will appear to clog/obstruct your engine cooling tins.

To clean out more of that carbon buildup in your head, you can use EZ-OFF oven cleaner or the purple Kleener/degreaser sold in the automotive section of automotive stores and Wal-Mart (if those are in your area). Be sure to wear rubber gloves and protective eyewear when using these chemicals. Just spray it and wipe clean.

I would get a new head gasket. Judging by the look of yours, you had some oil blow out. Be sure to spend the extra money to purchase Kohler parts for the head gasket......some of the knock offs do not have the wrap around the inside of the gasket and oil can leak through the layers of the gasket.

These are probably things that others have mentioned but my computer will not allow me to pull up the 3rd page of this post.....strange.....so, sorry if these are repeats of what others have already said.

One more thing, don't forget to re-torque your head bolts in the correct order after 5-10 hours of run time (I think that is correct......I forget, but it is mentioned in the manual).

Best regards,

Cub Cadet 123

The service manual recommends soaking the head gasket in water for a short time before installing.

Success!!
 

I finally got back to this last weekend and believe it was successful. Thanks for all the help!!!

I pulled the valves and cleaned everything up - valves, guides, head, piston, etc

Attachment 64225

Attachment 64226

Attachment 64229

(note the picture of the valves is from when I was about halfway through, I cleaned them up more before reinstalling)

I cleaned up the exterior of the engine as best I could and vacuumed/scraped out the 'insulation gunk'. I called it this because it was pink and really did look like insulation. Maybe some mice found it nearby and transported it?

Next, getting the valves reinstalled. Despite the warnings on other threads, I didn't buy a valve spring compressor, also had no grease on hand to help stick the keepers on. I tried it with screwdrivers and other implements for at least 30 minutes without even getting close to success. Determined to finish, I scoured the garage and invented my own spring compressor from an old caulking gun, hacksaw, a couple wood blocks, and duct tape:

Attachment 64228 Attachment 64227

It worked pretty great! Patent pending :cool:

I planed the head using the glass/sandpaper method as suggested (the pic above is from after planing) and installed with a new head gasket. I soaked the head in water for a short time before install. I cleaned up the head bolts with carb cleaner too. One was pretty gunked up, the others weren't too bad.

Torqued the head bolts per the manual, new gaskets for the valve breather & carb. Drained and cleaned the gas tank too. Put a little mystery oil in the spark plug hole and put in a new spark plug. Lots of bolting things back together and some new gas, reconnected the battery, and time to fire it up.

Turned the key and she started on the first try! Was a little smoky but I attributed that to the mystery oil.

I drove around for about 30 minutes. I changed the oil (SAE 30, had been using 10w30 in the winter) and retorqued the head bolts. Reinstalled the top piece of the engine cover and put on the air filter, ready to go! Started up easy and was running nice and smooth.

So, I went out and bought a leaf sweeper, tine dethatcher, spike aerator, and pull behind spreader on CL.

I used the leaf sweeper pretty intensively for 2-3 hours over the weekend. The engine ran great - it didn't stall out or backfire, ran strong at full throttle and idled real nice too. While this use wasn't as heavily loading the engine as the snow plowing where I had so much trouble in the winter, I think it's a pretty good sign I've fixed the problem.

Again, thanks for all the help! Next - get the mower deck fixed up :bigthink:

Nice compressor, and glad to here all that work paid off!!! Nothing like turning the key, firing right up and running smooth.