Kohler KT17 Overrev

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Jim Becker
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Kohler KT17 Overrev

Postby Jim Becker » Wed Oct 05, 2016 9:41 am

I was mowing the lawn with a Kohler KT17 (OK, it is a Deere 317) and it started to rev way beyond normal. The symptom seemed like the governor/throttle was sticking wide open. It would run normally until it hit a situation where it needed to fully open the throttle (heavy grass, increase ground speed, or steep up hill). It would respond properly to the demand but as soon as the load dropped it would rev up like mad. I could pull the control lever and it would slow immediately. It seems that the governor would slow it down if I let it go slightly longer than my reaction time.

I have fiddled with the governor-to-carburetor linkage and it doesn't seem to bind, but moves freely and there seems adequate spring tension to pull the throttle closed. I checked the feel both at idle and engine stopped and there was (to me) no obvious problem. The engine has about 200 hours on it.

Is there some KT17 quirk that I should know about? Does anyone have suggestions on what I should be looking at?

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Re: Kohler KT17 Overrev

Postby gitractorman » Wed Oct 05, 2016 12:10 pm

Jim,
Take the spring off of the governor linkage ot the carb and see if the linkage will rotate more than a few degrees. If so, and there's no stop, the tab has broken off inside the engine that the governor gear pushes on to actuate the governor. I've seen this happen in several Kohler engines, most of the time it results in a blown engine from over-revving, but it sounds like you have caught it in time. The governor arm should only move from about 12:00 to about 2:00 at most, any more than that and it's probably broken.

Bill
Cub Cadets 682, 1811, 1864, Simplicity Legacy XL 4x4 Diesel with FEL, 60" mower, 50" Tiller

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Re: Kohler KT17 Overrev

Postby Jim Becker » Wed Oct 05, 2016 11:41 pm

Thanks. That is the kind of insight I was hoping for.

The link from the governor to the carburetor on this engine is a solid rod with a bend on each end to go through each lever and keep it in place. While connected, the movement of the carb throttle shaft limits the movement of the governor shaft in each direction. Evidently, the only way the rod can be disconnected is to either remove the carb or remove the lever on the governor shaft. I decided to remove the governor lever. Since the position of that arm on the shaft is the linkage adjustment, I marked it with a marking pen so I could get the setting back.

Once the arm was back on, as close to the original setting as I could get it, the pictures show what I found on rotation. The first picture is with the throttle against the idle stop and the governor moved fully towards the carb. Movement of the governor was stopped when the arm bumped the air horn. The second picture is with both parts moved as far as possible the other way. The governor shaft hits a hard stop at the position shown. You can see the distance between the hole in the governor arm and the end of the link attached to the carb. My understanding is that they should line up when the governor and carb are both against the stop. Maybe I didn't get the arm as close to the original setting as I thought, but I don't think I could have missed by this much. There was no evidence from the dirt accumulated to suggest the adjustment has recently slipped. Is it possible that the part of the governor that pushes the tab of the governor shaft has failed or lost some material that changed the apparent setting?

It looks like getting inside the governor requires a total teardown to the point of splitting the block. Is that so? Since the governor shaft feels like it is still hitting a hard stop, I think I should hook the linkage all back up and make sure it is adjusted by the book. Then see what happens. Do you have any suggestions at this point?

closed.JPG


open.JPG

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gitractorman
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Re: Kohler KT17 Overrev

Postby gitractorman » Thu Oct 06, 2016 9:04 am

Jim,
Sorry, I did forget that the governor in a KT-17 and KT-18 engine is vertical rather than horizontal, however, you understood what I was saying and did the same test. It looks to me like the internal parts of the governor likely came apart, since the arm did stop by touching something inside. If it just spun free, I would guess that the tab broke off the arm inside. Unfortunatley, you do have to split the block to get to the internals. On the KT-17/18, there isn't even an oil pan to remove to look up into the engine, as the oil pan is a molded part of the block. REALLY poor block design in my book, but oh well.

The governor gear is a plastic gear with small weights attached to it which push a small button out to actuate the governor arm. My guess is the plastic gear failed and/or the weights came apart.

On the older K-series, vertical shaft Kohler engines, there was a bulkhead fitting where the governor arm went into the block, and you could pull the arm out the side of the block without disassembling the whole engine. I cannot remember if that same fitting is used on the 17/18 block, and can't tell from your photos.

If it were me, I'd try to follow the engine manual and re-set the governor linkage / adjustment according to the book, as you've suggested. If that doesn't work, take a closer look at the block to see if that bulkhead fitting is present, and can be removed from the top. If so, you might be able to see into the engine with a light, or a bore scope.

Let me know what you find.
Bill
Cub Cadets 682, 1811, 1864, Simplicity Legacy XL 4x4 Diesel with FEL, 60" mower, 50" Tiller

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gitractorman
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Re: Kohler KT17 Overrev

Postby gitractorman » Thu Oct 06, 2016 9:17 am

Jim,
I just looked at an engine manual I have for the 18 Magnum engine, same block as the KT-17, and it looks like the governor shaft is actually bent L shaped, rather than a tab being spot welded to the shaft like in the older K-series engines, so, I'm definitely thinking that the gear came apart instead of the tab bending or breaking. I'm not sure if the KT-17 had the same governor arm as the M-18, but most things on the 2 engines are basically the same. Sorry, but if your adjustment doesn't prove successfull, you're likely going to have to pull the engine apart.
Bill
Cub Cadets 682, 1811, 1864, Simplicity Legacy XL 4x4 Diesel with FEL, 60" mower, 50" Tiller

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Re: Kohler KT17 Overrev

Postby Jim Becker » Thu Oct 06, 2016 10:55 am

gitractorman wrote:The governor gear is a plastic gear with small weights attached to it which push a small button out to actuate the governor arm. My guess is the plastic gear failed and/or the weights came apart.


Probably right. My guess, since the governor seems to mostly work, is that maybe it is operating on one weight or the gear failed such that one weight is sticking or a similar problem.

Kohler calls the governor shaft a "governor cross shaft" even though it is vertical, maybe because it goes crossways in the earlier designs??? The reference material I have seems to show the shaft bent to make a lever rather than a spot welded tab (although they show a tab for generator applications!). I don't think this block has any other fittings/panels/covers to get a view inside. The oil filler goes directly on top of the gear. Maybe if had a borescope (next purchase?) I could see something through it.

My next step is going to be to reassemble and adjust the linkage. Then I'll start it up and run it outside to hose all the crud off. After that I'll be able to see a little better how it is put together and if there is any other way to see what happened. By the time I do that, I'll know whether the fresh adjustment fixes it or not. My bet is no fix and I have a new project that will probably take all winter.

You would think Kohler could make an engine that would run more than 200 hours before it needed a complete tear-down. It wouldn't have cost that much to make the governor separately removable or make a more durable gear/weight assembly.

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Re: Kohler KT17 Overrev

Postby Jim Becker » Thu Oct 06, 2016 10:24 pm

Problem solved. It was kind of a dumb thing but I can't claim all the credit. The engine has a cylindrical air cleaner housing with a dust unloader that sticks down on the opposite side of the throttle linkage from the air horn. (I think it is a Deere design.) The housing has always had this tendency to rotate by itself and interfere with the throttle linkage. Whenever the engine speed does something weird, the first thing I do is grab the air cleaner and rotate it to the normal position where it doesn't interfere. That was my first reaction to the overrev situation. The air cleaner didn't seem to be out of place and moving it a little seemed to have no effect.

After getting the tractor back into the shop, I pulled off the air cleaner so I could see what was going on. The linkage seemed to feel OK, as I had reported in the first post. After unhooking the linkage, reassembling etc, I adjusted the linkage. By the way, after properly adjusting it, my index marks still looked right. A quarter inch at the end of the governor lever doesn't amount to much at the diameter of that shaft. The movement all still seemed good at this point. I put the air cleaner back on and started to get some odd binding. I rotated the air cleaner to make sure it was in in a non-binding position. It seemed to have some effect but didn't cure it.

Here is what I finally figured out: In the past, I had found that with the air cleaner wing nut good and tight, it typically would not rotate and cause a problem. Tight enough is about as tight as I can turn the wing nut by hand. Turns out, the bottom of the air cleaner housing isn't sturdy enough to stand up to being this tight. It had gradually deformed (and gotten a couple cracks) so the outer edge of the bottom was pushed lower than the original location. The deformation has gotten bad enough for the throttle linkage to touch the bottom of the air cleaner, causing binding. I have flattened the bottom and the interference is gone. Engine speed is now responding normally. With the air cleaner back to normal, there still isn't much clearance with the linkage. I need to come up with a better fix.

Bottom line, I should have realized that the binding went away when I originally removed the air cleaner. It had been rotated to a position that had never been a problem. But it was still the problem.

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gitractorman
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Simplicity Conquest
Simplicity Legacy 4x4 Diesel
Mitsubishi MT180D 4x4 Diesel
Circle of Safety: Y
Location: Grand Island, NY

Re: Kohler KT17 Overrev

Postby gitractorman » Fri Oct 07, 2016 7:38 am

Jim,
Glad to hear it was that simple. These engines are not the "friendliest" to work on, so I was really hoping that it was something easy. I actually got rid of my last Cub Cadet 1811, mostly because I didn't like working on the engine. It had been completely rebuilt, and ran great, but every now and then it just acted really funny, blew a big puff of oily smoke, caughed, then went back to normal. I just lost my confidence in it, and a newer Cub Cadet 1862 came along with an 18hp Kohler Command engine, which had really low hours on it, so it was time to move on.
Cub Cadets 682, 1811, 1864, Simplicity Legacy XL 4x4 Diesel with FEL, 60" mower, 50" Tiller

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Re: Kohler KT17 Overrev

Postby Jim Becker » Fri Oct 07, 2016 12:09 pm

I have had this garden tractor since 1982. When I got it, the seller (a dealer) said it was "about 2 years old". He said he thought the engine had been replaced. Deere replaced a lot of these engines under warranty. He also said the original owner had traded it for a model 400, which seamed reasonable. Years later, I checked some of the numbers and found that "about 4 years old" would have been more accurate. The engine did check out as newer than the tractor, but still a Series I engine. That engine never was quite right. It always burned a little too much oil and one spark plug liked to foul.

One day in 1997 or '98 something happened internally. I no longer remember the exact symptoms. It made some horrible noise and it either quit or I quickly shut it down. I drained the oil and found a piece of a gear partly blocking the drain hole. After much research and thought about what to do, I bought a whole new Series II engine. I never opened the old one up to see what happened, just stripped some potentially useful parts off the outside. Eventually I gave it to another person that had a bad KT17. He had a bad cylinder and this probably still had at least one good one. I installed the new engine in the spring of 1998 and added an hour meter at the same time, so I have an accurate measure of the 200 hours on the engine. A side benefit of the whole new engine was to replace all the engine sheet metal that had accumulated a large number of vibration cracks. Whoever decided to call these things "quiet line" must have been a real comedian.


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