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I currently mow about 2 acres with a 42" Scotts mower powered by a Kohler CV15S. It's been well maintained and has been running fine. Yesterday, just as I was finishing up, the mower quit running. I expected that I was out of gas , as I had been mowing for a few hours, but the tank still had plenty of fuel left. I went to restart, and it fired right up.....but with a loud "clanking" sound. I quickly shut it down, and decided to let it cool, while I went to trim. Restarted later, and the loud clanking is still there.

I haven't had much time to dig into it (had a storm come through and downed a tree across my driveway), but here is what i know:

• Engine has been running fine up to this point, no hint of trouble
• Oil level is fine; oil is clean
• Pulleys on the underside are tight. Had them come lose before, and it makes quite a lot of noise as well

Here is a quick video recording from my phone, although the "clanking" sound seems to be much more noticeable in person.




So, what do you think? Is this a knocking rod or possibly something else?

Don't run it anymore.
If it throws a rod, you won't have anything left to fix.
What kind/viscosity oil have you been using?
Where in Ky. are you?

10w30 through a Purolator One filter.

East central KY, near Mt. Vernon.

I agree, don't run it until you diagnose it, sounds more to me like a push rod.

On these engines I have seen the carb's throttle plate screws fall out and get sucked into the engine, yours kind of sounds like that. The screw would be imbedded in the top of the piston if that was the case.

Fish said:

On these engines I have seen the carb's throttle plate screws fall out and get sucked into the engine, yours kind of sounds like that. The screw would be imbedded in the top of the piston if that was the case.

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Thanks.

I pulled the valve cover and I did'n't see any red flags. Rotating the engine by hand, everything seems to work as it's supposed to.



I haven't pulled the head yet, but it does look like one of the small screws that holds the carb butterfly on is missing. (click on the image to get to a full size version and you can see it better).



What kind of damage is that little set screw likely to have caused to make this thing clang so loud?

Just pull the head and pluck the remains of that little booger out, and reassemble, and Loctite all of the carb screws.

Well, I messed up. Got in a hurry and rounded off the corners of one off the head bolts. So, the head is not coming off without a lot of work.
I may just put it back together and hope for the best.

To be honest, it will probably pound on in or break apart. The only serious loose screw failure was on an old Tecumseh OHV.

He heard a loud whack, and it shut down 10 foot later.

When the piston hit the screw, the rod cracked up and shattered shortly thereafter. Put a new rod in, he was good to go.

The only real danger is if the screw is near the edge, and it might be a bigger problem.

But you definitely need to locktite in your carb screws.

Just wondering if this engine has counter-balance gears or weights that might be clanging around? I worked on an old Kohler 14 HP side shaft cast iron engine that had 2 counter-balance gears in it. Found some teeth in the oil drain pipe! That means the counter-balance gear is jumping up and down and could possibly lock up the engine and destroy it should more loose teeth get wedged in something. It would run, but clang like a mule kicking in a metal stall. It's been shut down for now and repairs delayed for a winter shop project .

Silverleaf,
MY 2002 JD LT150 Kohler CV15S just came up with this same problem over the weekend. Started and continues to make the exact same sound as you provided in the uploaded video. Began as I was finishing up a very short run. Did you ever come to a find diagnosis of the underlying problem? What was the remedy?The machine has been perfect until this. All maintenance was carried out on schedule.

I look forward to your reply.
Thanks.

Bavanrauser said:

Silverleaf,
MY 2002 JD LT150 Kohler CV15S just came up with this same problem over the weekend. Started and continues to make the exact same sound as you provided in the uploaded video. Began as I was finishing up a very short run. Did you ever come to a find diagnosis of the underlying problem? What was the remedy?The machine has been perfect until this. All maintenance was carried out on schedule.

I look forward to your reply.
Thanks.

Click to expand...

It was exactly as Fish said. A throttle plate set screw came loose and got sucked into the intake. I couldn't remove it without a great deal of work because I rounded off a head bolt when I got in a hurry taking it apart. Long story short, I replaced the screw, and have been using it as-is ever since. I believe the screw has been pulverized by now. Everything seems fine, and it has gotten a lot quieter. I mow close to 1.5 acres with it, and its been fine so far.

Yeah, that little screw is likely pounded deep into the piston, or else blew out the exhaust. Thanks for getting back with the results, these guys here don't believe me most of the time..........

HI, I'm new to the forum. I wanted to share something that happened to my mower last week. Same as others have posted on this, finally discovered that one of the throttle plate screws got sucked into the engine, made a terrible knocking noise. Was quite convinced it wasn't a rod due to the pitch, but my local John Deere dealer thought it was, as I had recorded a short clip for him to hear. An online search brought me to this forum and the prospect of the throttle plate screw seemed very likely, and after verifying that a screw was missing in the throttle plate, in I went. Sure enough, the screw was embedded into the head and a dimple was formed in the piston. So a few hours later with a new head gasket, exhaust gasket, new throttle plate screw (with #609 LocTite, on both!) and oil change it is up and running smoothly again. Thanks for all the great information that is posted here, I will keep an eye on this site regularly!:smile:

Fish said:

Yeah, that little screw is likely pounded deep into the piston, or else blew out the exhaust. Thanks for getting back with the results, these guys here don't believe me most of the time..........

Click to expand...

Seen it more than once, just as you describe.
Even seen one that had gone into the piston thread side down and the customer thought it was supposed to be there.

bertsmobile1 said:

Seen it more than once, just as you describe.
Even seen one that had gone into the piston thread side down and the customer thought it was supposed to be there.

Click to expand...

HI Guys - Im new here as well. Like Silverleaf, I own a 2002 JD LT150 Kohler CV15S. Great machine, very well cared for, but it suddenly developed a bad knock last time I used it. Sounded like a push rod problem, but I Googled around and watched several "Taryl's" videos on youtube. Taryl mentioned the screw issue in one vid, and I learned more about it here as well. Long story short... I have the same exact issue! When I read about the issue here and then saw that one screw was missing on my throttle plate, I pulled the valve cover and then the head, and found the screw which has beat up the piston rather badly, lodged into the cylinder head. (see pics enclosed). I plan on cleaning that head and piston up, replacing the gaskets, etc, and Im hopeful that the Kohler comes back to life. "Mr. P" and others - thanks so much for your post and pics, they really helped me diagnose this strange issue.

Just hope your piston rings aren't pinched... It may smoke quite abit. Only one way to find out.. Unless you remove the piston.

I had one real old tecumseh once suck in a screw while mowing. The rod just disintegrated, everything else was fine.
Put in a new rod, cleaned up everything, replaced/loctited the carb screw, and the thing ran like new.