Spun Crank Seal

blsnelling · May 18, 2012

I was working last night on a 365 converted to 372XPW. It wouldn't idle down but tuned nicely on the high end. Even though the H tuned fine, I finally went after the crank seals. The PTO side seal was just laying there, completely loose! I think the bearing has spun as well, as it's loose. Anyone ever seen this on a 372? How does a seal get loose like that?

BTW, this is a hard worked saw belonging to a tree removal company. These are the same guys that had the MS460 with the bad PTO crank bearing that I just rebuilt for the charity drive. Is there a connection somehow?

WKEND LUMBERJAK · May 18, 2012

Could be a connection, I've been around some guys that could break a prybar in a sand box.

Work Saw Collector · May 18, 2012

Always running chains to tight?

Jacob J. · May 18, 2012

Work Saw Collector said:
Always running chains to tight?

Running chains too tight combined with forcing a dull chain to cut. It builds the heat along with putting stress on the stub shaft and bearing pocket.

Stihl Wielder · May 18, 2012

Interesting find, Brad, with some interesting ideas to figure it out! I have an old 015 that I can't get to idle down either, have tried multiple carbs, rebuilt carbs, etc. I think it may be the crank seals but I cannot find any replacements out there. Anyone know where I can get some Stihl 015 crank seals?

Dan_IN_MN · May 18, 2012

So the bearing failed because probably running chains too tight? The failed bearing probably pushed out the seal. I personally don't think there would be enough friction between the seal lip and shaft to spin a seal.

Do you have the saw apart yet?

blsnelling · May 18, 2012

No, it's not apart. The seal did not push out, it actually spun in the case, such that it just falls in and out of the bore, with no resistance at all.

blsnelling · May 18, 2012

Jacob J. said:
Running chains too tight combined with forcing a dull chain to cut. It builds the heat along with putting stress on the stub shaft and bearing pocket.

Makes perfect sense. "Gotta get this job done, don't have time to sharpen the chain!"

Tzed250 · May 18, 2012

Just have Nik put a sleeve in it.

blsnelling · May 18, 2012

Tzed250 said:
Just have Nik put a sleeve in it.

I've already got a case, bearings, gaskets, and seals lined up. The price was right :rock:

Tzed250 · May 18, 2012

Can't beat that!

tlandrum · May 18, 2012

brad my number is my sig.call me and i can tell you a quick fix for the seal. as long as the bearing didnt spin i can put that back in service pretty easy.

Dan_IN_MN · May 18, 2012

tlandrum said:
brad my number is my sig.call me and i can tell you a quick fix for the seal. as long as the bearing didnt spin i can put that back in service pretty easy.

opcorn:

Dan_IN_MN · May 18, 2012

Tzed250 said:
Just have Nik put a sleeve in it.

I had thought about that too!

blsnelling · May 18, 2012

tlandrum said:
brad my number is my sig.call me and i can tell you a quick fix for the seal. as long as the bearing didnt spin i can put that back in service pretty easy.

I won't know until I get it apart, but the bearing is either shot, or it's spun in the case.

tlandrum · May 18, 2012

if the bearing has not spun it is easily fixed to hold the seal again without having to insert a sleeve. this is as ong as they didnt run it too long this way.

Dan_IN_MN · May 18, 2012

tlandrum said:
if the bearing has not spun it is easily fixed to hold the seal again without having to insert a sleeve. this is as ong as they didnt run it too long this way.

So....the seal can work loose with out the bearings help? What's the fix? Was the seal not put in far enough to begin with?

tlandrum · May 18, 2012

i had one spin the seal in the case not to long ago without the bearing being bad. i guess it just happens to be something thats not that uncommon. you can take a center punch and punch the case around the lip of the seal boss. there is a raised taper on the outside of the case around the seal mounting surface. if you center punch the case lightly about 1/8 apart all the way around the case it will shrink the seal boss and will now hold the seal tightly again. you need to use some three bond along with the seal to make sure of no air leaksbetween it and the case. hope this helps sombody save a case some day.

Spun Crank Seal

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