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Chris727

Blown K341, What happened?

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Chris727
Hi Guys! Last year I picked up an MF16 for free with a hole in the block. I am just now getting around to swapping in a good engine but was curious as to what caused the old one to blow. The engine had sufficient oil in it. Engine fins were dirty but nothing too extreme. There were the remains of something small that died in the blower cover. The cam had been forced back and broke the block out under the carburetor.

As I tore it open I found this.

The rod had broken into many pieces. Fortunately the crankshaft was not damaged, the crankpin measures with no wear. The part of the rod still attached to the crankpin had no scratching or visible problems.

The cam broke in several places.

The piston was somewhat discolored.

The cylinder was still standard bore but had some wear, the engine was probably using a little oil. The head had some whiteish stuff underneath. Is this an indication of overheating?

I am also wondering if its possible the cam blew first, then caused the rod failure? Thanks in advance. Chris

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Al
Hi, The real clue here is the rod broken at the wrist pin. The break at the crank pin is secondary. Rods broken from over reving almost always break at the small end of the beam, near the wrist pin. The fact that the crankshaft has no metal transfer is an indication that it is not a lube failure. Check out the governor, or maybe someone was just "reving it up" by hand with the governor linkage. Al Eden

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Ronald Hribar
I too received a tractor because "Kohler Blew" However when i took it apart rod ,crank and block were good. And cylinder bore was good, rod bearing and crankshaft journal looked good. So I put in a new rod and piston. When i went to rotate crankshaft it would turn 1 3/4 turns and stop. Took rod and piston out, checked orientation of oil hole in rod, put back together same thing I gently pried on several internal components and crankshaft rotated freely. I did not trust myself to put it togeether, took it to dealer who is putting it back piece by piece checking each component. There are members here that are very experieced with Kohlers who may shed some light on this problem.

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D-17_Dave
Welcome to the world of Kohlers. This, for several diff. resons were a common problem with the 341's. I tend to think from seeing so many broken in the middle of the rod with no other distingwishable damage until the rod started beating around in the block that the rods were somewhat weak. It (to me) seems almost any operation outside the designated operating range usually results in this condition. Over revving, temp. varying outside the normal temp. range under load in some wear patternes could cause the piston to bind from lack of lubrication from the high temp. or lack of oil puts tremendous stress on the rod with running. Even if it weren't hot enough to cause damage or metal transfer it could have been putting more than normal stress on the rod. Part of the point is no one may ever be able to tell each case for sure. But the cure is to replace it w/ a Briggs.

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Guest
I thought the MF16 used a Tecumseh engine. Were both Kohlers and Tecumsehs used or did I just read something wrong?

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Al
HI, I have a book by Briggs on failure analysis, from a class I took. I am trying to get permission to post it here. Hope it works out. All 3 Brs Koh and Tec all teach small end rod failures are usually caused by overspeeding. (Usually overheating causes piston failures or the oil gets so hot that you see lube failures on the crank pin.) Then the rod is free to flop around and wipe out other things in the area. This is not absolute, but how they settle warranty issues. Al Eden

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Chris727
Beeser, The MF 7 through MF12 used tecumseh engines, these are some of the most commonly found MF garden tractors. The MF14 and MF16 (same except for HP) are a much larger tractor and were produced in the 70s. They used Kohler engines as did many of the Snapper-Built Masseys of the 1980's such as the 1650s etc. Thank you to everyone for all the great info. Al, this engine is a 1975 according to the serial#, so the rod and piston must have been replaced at one time. I know someone had it apart because of all the gasket sealer on the pan gasket. Thank You! Chris

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