One for the Kohler experts Update

[Brettw]

Well, I got ambitious and pulled the hood off of the recently acquired Sunstar. As I stated in an earlier post, I had pulled the heads due to no compression, when the engine was still in the tractor, and observed no valve train movement, but smoothly turning crank and pistons. So I pulled the M20, and tore it down. I was expecting the infamous broken governor gear and hence the camshaft. Now here is where it gets interesting, or strange, however you want to look at it. This is a replacement engine and not too old. The inside was spotless. But here is what I found: The governor gear was intact. The valves and lifters were completely fine, undamaged and moving freely. Everything looked fine, until I rotated the cam shaft around. The cam was stripped of a half a dozen or more teeth, in one area. Hence the crank could spin, but the cam did not. Governor gear shows a bit of wear and damage from the bad cam, it will be replaced. The crank fared OK but has some slight scuffing. No other internal parts appear to have been damaged. Even the fiber oil pump gear appears to be fine. The missing teeth on the camshaft didn't appear to interfere with anything. Amazing.

So, what would cause such a failure? It appears as though, for whatever reason, the camshaft had a good 6-10 teeth (all in a row, the rest is perfect) sheared off? I haven't seen or heard of a failure like this before.

[PhanDad]

I have no clue.

But a WAG - a BAD backfire??

[Brettw]

Bill,

The PO was cutting grass just like normal when it made some noise, not according to him catastrophic, and he shut it down.

I am truly at a loss. The internals are spotless, and I cannot see any reason for failure that is apparent. Other than the teeth from the camshaft, there is nothing else I can see that has failed. And (a major plus), nothing appears to have been damaged by the teeth from the camshaft. Perhaps a bad casting? But nothing appears, upon close inspection of the gear, to be a void in the casting at the failed teeth. Weird. Maybe if there was some sudden stop in the valve train, but all of that is clean, moves freely and is undamaged. I don't get it.

I have a replacement camshaft, and a crank. I will order a new governor gear assembly off of e-bay, Gaskets/seals, and it should be ready to reassemble.

Whenever I see failures, I look for WHY. When I hear about seals blowing out, I say " look at breather problems". Why are you having issues with seals, there must be an issue causing it. In this case, I don't see the issue that may have caused the failure of the cam, so I am curious and confused, and am concerned about putting it back together if I am missing something.

[Burntime]

Brett, I had a kohler in a case that the crank literally split. Sometimes when its time, its time. No ryhme or reason. Good news is it sounds like with your skills it will be up and running soon!

[Brettw]

quote:Sometimes when its time, its time.id="quote">

id="quote">

So far, that's the only explanation that might make sense!

[Burntime]

Brett, not everything makes sense. Thats part of this stuff that makes it fun. Trying to find out the who, what, when, where, why. The bottom line is it could have been much worse and it sounds like an easy fix, at least for you! Winner winner, chicken dinner!

[Brettw]

Well, waiting for the governor gear to show up and it's ready to go back together. The cam and crank I had are in good shape and it all dropped back together. In the detailed cleaning mode and partial reassembly, I saw nothing out of place. There were actually 5 teeth taken out an the cam, and all 5 are accounted for. So, clean as a whistle and waitin' on parts..............

[steve-wis]

My guess is one tooth failed, for whatever reason, and the pc that broke off then jammed into the one next to it, and on and on, until a big enough space was cleared of teeth for the crank gear to not drive any more. Sometimes they may have stress cracks from heat treating that will eventually fail. This is my best guess.

Steve

[Burntime]

quote:Originally posted by Brettw

Well, waiting for the governor gear to show up and it's ready to go back together. The cam and crank I had are in good shape and it all dropped back together. In the detailed cleaning mode and partial reassembly, I saw nothing out of place. There were actually 5 teeth taken out an the cam, and all 5 are accounted for. So, clean as a whistle and waitin' on parts..............

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id="quote">

id="quote">Sounds like you got lucky! Congrats!

[Brettw]

Back together and purrs like a kitten, the only parts I had to purchase were a new governor gear, as it got a bit beat up when the cam went. I had a camshaft, and a crank. Rings still had .010 end gap, so nearly new specs. everything else was clean and solid, and I took it out for a few laps. Interesting that with all the potential catastrophic issues that could have taken place, it was just 5 teeth on the camshaft, all all were recovered intact. Something different every day.....

[PhanDad]

Let's hope for 30+ years of purring!