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Discussion Starter #1
Hi yall. New here and i got a problem I was hoping yall could help with.

The tractor I bought last week for mowing my lawn, it's got one **** of a misfire. It's a Kohler 15.5hp (cv15s, spec no. 45108) in a craftsman tractor (917.257660). It sounds smooth at idle but when you bring the RPMs up to drive and mow and it chugs and belches black smoke. I took it out tonite and it smoked pretty good the whole time. Just doesn't seem to have much power either. But then at one point it came to life, sounded really good, no missing, no smoking, and ran great with a ton of power. But that only lasted about 10-15 seconds and went back to the weak smokey chugging again. A few minutes later it started to rain so I put it back in the garage.

And I was just out and pulled the red cover off the engine and found a few things, first off, the head was packed full of grass clippings, fur, and other junk, guess a rodent made it home for a while, the plug is fouled but looks to be new other then the thin layer of soot on it, checked the AF again, and found that the prefilter wasn't just tore a lil bit like I thought before, it was eaten, plus when I pulled the prefilter off (didn't do that prior) the air filter is horrible. Also found that the coil and contact of the I guess flywheel was severely corroded. I used a lil emery cloth and lightly knocked the big stuff loose and finished with a wire brush, but the coil slides back and forth and now it's outa adjustment. It fired but ran a lil worse than before. So I guess I need the specs on adjusting that, pick up an AF and a plug, and go from there. also cleaned out the head.

Here's a vid from before I messed with it tonight



Anyone here have an idea why it's running poorly other than the plug and air filter? I don't think the AF would couse a misfire, plug could though, but I think there is more to it. I really need to get this grass mowed if it ever stops raining.

Thanks in advance for any and all help,

Ron
 

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Black smoke and sooty plug usually means it's running rich. Are you really sure the air filter isn't plugged? If it's not, then you may have carb issues, hopefully as simple as adjusting the main jet. I don't know what the spec on the coil clearance is, but a business card thickness should get you in the ball park.
You might try starting it without the air filter, although you should make sure nothing flammable is around in case of backfire through the carb.
Let us know what you find, lots of help available here :thThumbsU
 

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I know this may seem elementary, but what position is your throttle lever in when this is occuring? My old craftsman with the Kohler 14.5hp had no paint/decals left on it, so you couldn't tell where to have the throttle position for mowing. If your pushing the throttle lever all the way up, then you have the motor choked. If you look closely at the throttle lever, on the left side of the arm you will see a small groove. When you bring the throttle up, a detent engages into that groove. When it's in that position, it is meant to be at max throttle. Anything past that and you are choking the motor!
:thSick:

Good Mowing!
 

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Discussion Starter #5
No, it's misfiring, not just running rich. The richness is due to the misfire.

It happens at all RPMs just over idle. Check out the vid, you can see/hear it. And no I'm not choking it. Only to start it. I do understand somethings about small engines, just don't know how to figure this misfire issue out.

As for the valve seat, there is no noise from the engine. That should cause some sort of a knock.

Fcubman, Like said in the first post, the air filter is bad, which could cause a rich condition, but not a misfire.

Thanks so far yall.
 

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How long was it since it last ran? Sitting all winter with fuel in it is not good. I'd clean the tank , lines, and flush the carb first. Give it a thorough cleaning. Blow out all the ports as best you can. I would think that'll cure the problem. If not my next guess would be spark from the coil. I've replaced a couple coils on Kohler Commands like yours before. Let us know what you find.

also, as one Seebass322 mentioned, check the actual throttle position on the engine compared to the dash. Make sure full throttle on the dash isn't pulling the choke linkage closed on the engine. The linkage on the engine is adjustable if I remember corectly. I listened to your video and it does sound like the choke could be half closed. My .02 :trink39:
 

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Discussion Starter #7
The people I bought it from said they mowed with it the week before. Then when they tried the week I bought it, they said it wouldn't start. He did clean out all the fuel system but still couldn't get it to run. I found that the wire on the fuel shut off solenoid on the bottom of the carb, the terminal on the solenoid was broke but I managed to get the wire back on. Also the main plug from the chassis to the engine the contact were corroded really bad causing a loss of connection to the solenoid so I took it apart and cleaned that.

I have watched the linkage on the engine vs the lever on the dash, everything seems ok there.

I keep thinking is electrical in relation to the coil. The coil seems to fire just not each time the magnets/contacts on the flywheel pass.
 

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Sounds like a lot of underlying problems. I'd take the carb off and clean it good, then install all the new stuff, put some Seafoam in the tank and see if all that helps.
 

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Discussion Starter #9
Ok this thing is making me mad now. Got home from work, double checked the choke and linkage, all good. But now I can't even get it to run. Took the air filter off, and it spits raw fuel up outa the intake and occasionally a lil ball of fire. Also I pulled the plug out to check if it was sparking and it barely does but when I pulled the plug off the side of engine while it was still spinning I found the coil is working :duh: At least the shock from it ain't as bad as a Hi-po coil and an MSD box in a built mustang :ROF

So I'll pick up a plug and an air filter probably tonight or tomorrow and try again. Guess I'll get a couple plugs to be safe.

But this thing is acting like a car that the timing is out on. Been there done that many times, but these lil engines don't have a distributor to adjust so I'm at a loss.
 

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If it is acting like timing check the shear key on the flywheel but sounds like high idle circuit is dirty hope this helps Doug
 

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And gas comming back out the intake is an open valve probley hung up on the loose seat...
 

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Discussion Starter #13
Ok, tinkered with it some more, made no progress. But I did notice a black and a yellow wire, both about a 12 gauge, that go under the flywheel. Any idea what these are for? Also how do you remove the flywheel to check the key? I assume its the same as a woodruff key that holds the crank pulley on a car engine. I took the center bolt out of the flywheel, but it wouldn't come off and I didn't want to force it for the change screwing something up worse.

If I don't figure it out by saturday, a buddy of mine that used to rebuild and repair Onan gensets said he'd come over and take a look.

Doug, what is the high idle circuit you mentioned?
 

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The wires under the flywheel go to the chargine stator, dont bother them...

A few suggestions.

Pull the vent hose off of the valve cover, and try to run it a bit...sometimes gas can accumulate in the oil and the fuel vapors will actually travel from the crankcase, up that hose and make the engine run a little rich and misfire.

A bad coil can cause what you are stating it is doing.

Could be a problem in the carb from the previous owner "cleaning" it out.
 

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Discussion Starter #15
Well it turns out it wasn't anything I would have though, and nothing anyone mentioned anywhere I posted it.

The carb was cracked. Guess when the previous owner over tightened the fuel solenoid he not only stripped the threads, he split the carb where the solenoind goes in.

So we used some putty stuff I had that cures to the hardness of steel and filled the crack and now it runs great. No smoke, smoother, quieter, and rpms are much higher. Even went through foot high (some places higher) grass with little trouble.

But thanks yall for trying to help.
 
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