Crank failures

[PES+]

I tried to get these pics so you can see the differences but they are quite low hours and the metal reflections makes it hard to get pics

Which crank failed which way?

 

[Four Paws]

The crank on the left:

Large end bearing got hot hot hot! Straight gas??

The crank on the right:

Broke the big end of the rod. Would assume bearing failure on this one - due to rust??

 

[gunnarfan]

to... or not to ... that is the question

so are you really asking when its ok to yank a crank?









"I figure a man's worth about 18 an hour chum...." Bob Avery

 

[bump_r]

Looks like someone dipped 'em in sugar.

 

[Dan Forsh]

I can understand how the one on the left got like that and it looks obvious due to the blueing of the metal, but how does a conrod break like the one on the right?

 

[AZLOGGER]

The crank on the left: 372 Crank
A. Insufficient lubrication.
B. Ran WOT under no-load condition too long.
C. Overreved.
D. Carb adjustment too lean HI side.
E. Air leak thru faulty seal.
F. All the above.

The crank on the right: 385 or 390 Crank
A. Insufficient lubrication.
B. Bearing cage failure.
C. Overreved.
D. All the above.

IS THERE A PRIZE FOR THE CORRECT ANSWER CAPT. RON?

 

[AZLOGGER]

PEST:

Do these pictures look familiar?
I had a little insight as to what your problems were.

I believe they lost their virginity.


Oh by the way you STIHL lovers I have some MS 440's & MS 460's that look just the same.
:deadhorse:

 

[PES+]

Neither of these two saws had any piston damage at all.

Neither saw was overrevved nor run too lean as confirmed by position of adjustment screws and both had proper oil mix

They are Jred versions not that it matters

 

[PES+]

Both saws are back out with their original pistons.
The one bearing left on the crank caught a piece of big end cage inside it and it came out of the case on disassembly so it was replaced. The other side was fine. The seals on both saws were like new no damage but the seal on the replaced bearing side was replaced due to need to heat the case to accept the new bearing.