Kohler Comand CV16S with engine knock

[enginemedic007]

Hello folks,
I have a 1999 Dixon ZTR with a Kohler CV16S, Spec #43516 serial number is tough to get as the first 2 numbers are missing as that part of the sticker is missing, but it looks like _ _ 31012751, it looks as tho it could be a 98, or a 23 or 28. As near as I can figure the Mower itself is a 1999 Dixon.

This mower and engine were given to me, by a friend who claimed that the motor was seized. It sat in his yard for 6+ months before it was given to me. I had it in my garage over the winter was going to get it going. I started reading about these engines and getting my ducks in a row to fix it up and get it running. I started by pulling the blower housing off and the fly wheel would spin very freely, so i assumed that it was not seized. I then drained all the old gas out, and pulled the carb off and cleaned it, and put it back on, drained the oil out, the dipstick was just wet on the bottom of the stick with oil, i drained it out, and replaced the oil with 10w30 recommended by my local shop for the kohler commander with hydraulic lifters. replaced the air cleaner and the battery, attempted to start it and all went well. It started after just a few seconds of cranking and ran rough for about 30 seconds to a minute and then smoothed out and purred like a kitten...... I proceeded to warm up the engine and then slowly drove around my driveway and garage to warm up the transaxel and adjust it. All ran fine and seamed to be great. I parked it and waited for the grass to green up. Here in Montana that has just been in the last few weeks...... I have mowed my half acre lot, approximately 4-5 times as the grass was very long the first few times. Sunday evening i was mowing and was about half done, when the engine developed a knock, i had checked the oil before i started and it was at the recommended level. The day was high 70s low 80s while i was mowing.
So after that long winded explanation, my question is this, What could be the noise? I have read on other forums, that there was some issues with the push rods and air in the oil. Some folks said to add an oil additive, some said that's just the nature of the beast with this particular model of Kohler. I have an appt. at the local engine shop to ask them the same questions. Just thought i would jump on here and see what you fine folks could help me with. I dont have much money in to this engine, and am wondering also if its worth fixing it up or just scraping it and moving on. Everything on the mower and the engine seams very solid save for the normal wear and tear of a 15+ year old lawn mower.

I was a member of the PERR Fourm when it was going, and just never re registered on the new place here till now. Anyway, feel free to ask me questions if i have confused you, or you need more info. I will summaries the engine info below for you in case something wasn't clear.

Thanks again Tracy

Engine
Kohler Command
Family SKH426U1G2RB
Model CV16S
Spec 43516
Serial # _ _ 31012751
Has a serious knock in the engine after 5-6 hours of use, after fresh oil and filter change.

Mower
Dixon ZTR
4516K
Ser# 45-005985

[bgsengine]

Knock with the pto Engaged, or not engaged? - That is- knock there all the time, or just under specific circumstances?

Wondering if it might just be the PTO clutch banging due to a binding idler or spindle bearing.. or even a loose drive pulley on the engine crankshaft.. might help to eliminate those loads.. Could have a collapsed lifter, given the assumed hours it may have in it.. try a straight 30 weight oil perhaps, see if it still has the knock? Or it could be it seized up hot, and the rod bolts pulled their threads and are now coming out... if the rod is loose or a clearance issue with the rod you should be able to duplicate the knock when turning the engine by hand just as it goes through TDC or BDC , or when turning engine back and forth a little bit

[Deere2me]

What BG said............
PLus,I would try using Kohler branded oil first. I'm not a big fan of high priced mfg. branded oil, but some Kohler engines seem to like Kohler oil. Try it. Ya got nothin to loose, right?

[enginemedic007]

Thanks!

1. The knock is there all the time, when its started and at super low idol its not there at all, as soon as you move the throttle up it starts to knock. I can start it and run it. It knocks anytime its not at super low idol, by that i mean, an idol, thats just enough to keep it running.

2. What is the best way to spin the engine through TDC and BDC? is spinning the fly wheel ok? or should i spin the shaft down by pto clutch?

3. It has been a bit, but im pretty sure they local shop sold me the high priced kohler oil, they said the same thing that kohler stuff likes kohler oil.

Thanks again

[bgsengine]

Most of them, you can do palm of hands on the debris shield of the flywheel and roll engine by hand that way just rock it back and forth , but if as you say the knock is always there, it might just be a rod knock - but if you have a helper or spotter you or they can rock engine flywheel back and forth while listening/feeling to isolate the knock to inside the engine, or to some external component (which if you can access it or see it move, can hold it from moving while rocking engine and see if the knock goes away)

If internal, then quite likely you may have a loose rod (If you get the knock rolling engine back and forth) or when rolling engine by hand, you may get a knock twice per revolution , it may be the rod or crank - if the knock only happens in a certain spot (typically at TDC) it may just be carbon on the piston hitting the head, or it could be valve clearance due to a collapsed lifter , loose valve seats, etc - So it works best if you can try to isolate roughly where the knock is coming from by rolling engine over by hand - if necessary just pull the blower housing off for easy access to the flywheel, and go from there - usually working the engine slowly by hand to isolate the knock, you can generally identify (or an experienced tech can) what is causing the knock

On the other hand, if you have a fuel quality issue or excessive carbon, it could just as easily be a spark knock (Detonation/pre-ignition) from low grade fuel (unlikely, though.)

[enginemedic007]

Thanks so much for the help, finally had a chance to take the engine apart and it was a broken connecting rod, how ever when that broke, it did get in to the side of the cylinder, it's just a small "hit" to the side of the cylinder wall, about the size of half a quarter, It's right at the bottom, and well below where the piston rides. My question is this, should I/ can I just order a new connecting rod and replace it? Or can I have it machined down? And go with an over sized piston? Or replace the whole engine?
The cylinder, and piston and rings both look as good as new? You can still see some of the cross hatch from the factory in the cylinder. The journal needs just a bit of Emory cloth to shine it up. The wrist pin and all looks very good as well. From looking online, it looks to be about $150-$200 for parts to fix up. No idea on a new engine, or even if you can put a new different engine on.....

Thought?

Thanks again for your help folks, it's much appreciated!!

[bobodu]

Since it is your engine...just drop in a new con rod.

[enginemedic007]

So I don't need to worry about the chip/crack in the cylinder wall at all?

[bobodu]

Since it is below the rings, I wouldn't worry about it. Obviously, I can't see it from here. Just make sure the edges are smooth.

[enginemedic007]

Thanks for the help. Finally had some time today to take it to my local engine shop. They suggested the same so parts are ordered... Thanks for your help. I'm sure I will need more of it as this project progresses!