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K341 Piston Replacement, what else?

k341 broken piston rebuild acr automatic compression release kohler allis chamers 416

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#1 rjl OFFLINE  

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Posted March 08, 2015 - 12:20 PM

Last summer my engine quit and in taking off the head I found by turning the engine over by hand the piston would come up but not back down. I guessed the connecting rod was broke. Please keep in mind that I am not as mechanically inclined as I would like to be but not too long ago, with help from members on this site, I took apart and repaired things that I always thought were above my talents and had fun doing so. Now I want to fix this. I read through the service manual multiple times and read different forums on similar topics so now I am ready.?. I took the K341S off the Allis 416, popped the pan off the bottom and found that the piston actually split in half horizontally. The connecting rod and everything else seem fine. Both halves of the piston were still in the chamber and any fragment pieces fell into the pan, I could not see one scratch in the chamber. So I ordered a K341 rebuild kit with STD Piston, Rings and gaskets.

Now I am wondering if I should be replacing, or doing, anything else while I am in this deep.

This tractor was hard to turn over without a brand new battery or jumper cables. I read about the Automatic Compression Release and found that was not bringing the exhaust valve up like it should. I did bend the tab to where it works a little better. I will get a micrometer to be sure I have it adjusted enough.

I cleaned out the little carbon that is present, all and all not to bad from what I read.

I rechecked the gap in the valves since I am going to confirm the ACR is adjusted correctly. 


Is there anything else I should be checking, adjusting or replacing?

What do you think caused the piston to break?



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#2 greenb69 OFFLINE  

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Posted March 08, 2015 - 12:38 PM

In my over 40 years of working with engines I have seen this before but it is rare to be sure. It is more than likely, metal fatigue. If the piston split in a ring groove, this is more than likely the case. I have also seen them split at the wrist pin, another weak point. Sounds like you were lucky not having any cylinder damage. I would replace the rod for sure. You are in there and who knows what twisting may have worked on the rod. Not that much more cost to do it right. Give yourself more credit. You will do just fine on the rebuild.
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#3 rjl OFFLINE  

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Posted March 08, 2015 - 12:50 PM

Thank you for your reply and encouragement.
Do you recommend a sponcer of this site to order the connecting rod from? I ordered the piston rebuild kit through amazon.
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#4 KennyP OFFLINE  



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Posted March 08, 2015 - 01:10 PM

That's the 4th one of those broken pistons I have heard of in the last year or so. Have you checked to see if the bore of the cylinder is still 'STD.'? When ordering the rod, they will need the spec # off the engine. So get that. Most of the sponsors should be able to get you a rod. Maybe one will drop in here.

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#5 glgrumpy OFFLINE  


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Posted March 08, 2015 - 01:12 PM

Really best to order piston AFTER checking the wear on cylinder and they can bore to fit the piston you order then. You would need a machine shop for boring. OR, at least have them measure the bore and see how far worn?  Some of the kits come with rods, some not. It is better to have or borrow a ring expander tool for putting those on, and a compression tool for when putting piston/rings back into the block. Some stores rent or loan those tools out, or not that expensive if you plan another future build. Make sure rod is in right with hole for oiling pointing right way. Many miss that and have trouble when starting.

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#6 rjl OFFLINE  

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Posted March 08, 2015 - 01:27 PM

Thank you KennyP and GlGrumpy for your input.
For reference the spec # is 71106a for this engine. When I borrow the micrometer I will check the cylinder but I figured since there was no scoring and the piston was STD there would not be a need to measure?
I purchased the compression tool since I have all intentions of "having more fun later". I will look into a ring expander tool. I recall reading about the hole in the rod and have all intentions of following the Kohler service manual when putting back together.
I will keep this post updated with my progress, hopefully this coming weekend I will tinker some more.
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#7 boyscout862 ONLINE  

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Posted March 08, 2015 - 02:42 PM

It is good that you have read the manual a couple of times. Take your time. Read the B&S Repairmans Manual too because it has alot of good information that applies to all engines.Keep everything very clean. Test fit parts, then when you are finally assembling, oil the parts up good. In a way, I would recomend that you put this engine aside. Get a cheap lawn mower engine and overhaul it first. That way if something goes wrong it is not a big loss. You tube may have some help too. What ever you do, ask when you need help. Good Luck, Rick 


I see alot of the engine rebuilding tools show up at tractor and auto swap meets.  

Edited by boyscout862, March 08, 2015 - 02:43 PM.

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#8 Trav1s OFFLINE  


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Posted March 08, 2015 - 04:27 PM

Whoa... never encountered that before.  :watch_over_fence:

#9 rjl OFFLINE  

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Posted March 08, 2015 - 04:44 PM

Thank you for the advice. I doubt I will be tearing apart anything else before I put this back together. So far this is way easier than my first project. That was a transmission off a 67 MF10, I believe the member was Nutindon that wrote an excellent piece on that and answered a few questions I had. I have a couple local friends that I can also fall back on for help. One collects and the other used to pull tractors.
Thanks again.

#10 LilysDad ONLINE  


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Posted March 08, 2015 - 05:00 PM

Yup! Never assume,measure everything. Measure the crank journal while you are there. You don't want to have to tear that engine apart again in another year.

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#11 EricFromPa ONLINE  



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Posted March 08, 2015 - 05:08 PM

The Cub Cadet 129 I picked up had problems turning over after rebuild and I found that the ACR was slightly bent.I bent it back and it worked great for about a dozen startups then it started to crank hard again.


I'm guessing that it ran hot at some point and took some of the temper out of the thin ACR arm.I had a couple of used Cams so I took it back apart and swapped it out.It cranks much better and even starts a bit easier.

I did have to swap out the Cam Pin.There were signs of galling on the Pin and the cam fit loose on the pin.This engine had been rebuilt at-least once before It had been sleeved fairly recently.


The pto end of my crank was a mess to I ended up replacing the crank and put a full rebuilt kit in it.She's a really healthy runner now.

Edited by EricFromPa, March 08, 2015 - 05:10 PM.

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#12 rjl OFFLINE  

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Posted March 08, 2015 - 05:48 PM

I recall reading where some of these engine models are not made with an adjustable ACR. That if you try to bend it, it will break. And I recall mine being in that category but I figured if it did break it needed replaced anyway. I thought I got lucky but after reading EricfromPA's post... Maybe my engine did overheat tempering the ACR tab and weakening the piston in an odd placed. I will think more of this but at the moment if everything measures out correctly I will put this back together with the current ACR. Worst case with the ACR is most likely me taking this apart in a year or so. If this does work I have a Cub127, same Kohler engine family and same hard to start issue. That has a starter generator with all other electronics recently replaced. I would love for that to start nice in the winter... Thus could be a future topic of discusion, I am sure.

#13 FilledTires OFFLINE  

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Posted March 08, 2015 - 07:10 PM

Yup! Never assume,measure everything. Measure the crank journal while you are there. You don't want to have to tear that engine apart again in another year.


Agreed. Numbers don't lie. Measure everything while it's apart.

#14 superaben OFFLINE  

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Posted March 08, 2015 - 08:39 PM

If you decide to need a rod, which I do suggest you do, an aftermarket rod from me is $39. 


Ben W.

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#15 js5020 OFFLINE  



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Posted March 11, 2015 - 11:12 PM

Meh,, that's nuttin at least the bottom half of your piston in still in one piece and attached to the rod. The K341 in the WH was a 5 piece piston when I pulled it out year before last. Nothing else wrong that I could find and other than new piston, rings, rod, and gaskets it was good to go, only thing extra I did was to remove the "grenade gears" when putting it back together. Engine is a 73 and still STD, uses no oil, and starts with no effort even below zero,,,,, amazing for a 42 yr old engine.
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