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#Post#: 85941--------------------------------------------------
Oil seals on Stihl MS660 keep going bad.
By: emhusq66 Date: December 30, 2019, 4:49 am
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Hello Everyone, I am new here and this is my first question. I
picked up a Stihl MS660 at a estate sale (not running), I did
some research in the service manual and it says "saw is hard to
start, will not idle, runs fine in WOT". That is exactly what it
is doing, so it says to replace oil seals, which I have done now
3 times. When I start it after replacing the oil seals, it
starts on 2 pulls and runs great for awhile, then when I try to
start it again, same thing- hard to start, etc... I don't
understand what I am doing wrong (if anything). I did a leak
down test and it was still holding pressure after 20 min. I
really need this saw to run but I'm lost as what to do, any help
would be greatly appreciated, Thank you.
#Post#: 85942--------------------------------------------------
Re: Oil seals on Stihl MS660 keep going bad.
By: Chainsawrepair Date: December 30, 2019, 6:43 am
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Have you checked impulse line and replaced if old?
Had a 66 come in pretty much sounded like this and was just
impulse line.
Have you checked your crank bearings to make sure keepers on
both sides when doing seals?
Just making WAG's over net.
#Post#: 85944--------------------------------------------------
Re: Oil seals on Stihl MS660 keep going bad.
By: emhusq66 Date: December 30, 2019, 8:31 am
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First thank you for getting back to me so quickly I might check
the impluse line regardless of the new parts. The impulse line
is brand new and so are the main bearings which I put in myself.
Pretty much I tore the whole thing down and replaced everything
I could, I also added the big bore kit (56mm) and was planning
on buying a Hyway pop-up piston for the bigbore until all this
happened.
#Post#: 85945--------------------------------------------------
Re: Oil seals on Stihl MS660 keep going bad.
By: 3000 FPS Date: December 30, 2019, 5:27 pm
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When you say oil seals are you referring to the crank seals.
#Post#: 85958--------------------------------------------------
Re: Oil seals on Stihl MS660 keep going bad.
By: emhusq66 Date: January 1, 2020, 1:15 pm
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Yes Sir, the crank seals. Sorry about the delay.
#Post#: 85964--------------------------------------------------
Re: Oil seals on Stihl MS660 keep going bad.
By: 3000 FPS Date: January 1, 2020, 11:45 pm
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If the crank is smooth where the seal rides on it and the seals
are the correct ones then I do not see how they would go bad.
Plus you said you did a pressure test on crank case and it holds
pressure for 20 minutes. I do not believe the seals are your
problem. I would be looking for a air leak some place else
like cut4fun mentioned. The impulse or the intake boot and I
would even check the fuel line. Heck I would even suspect the
carb as possible problem too. Have you tried adjusting the
carb to see if you get different results.
When tuning a saw it can sure act different when it is hot as
apposed to when it is cold.
#Post#: 85967--------------------------------------------------
Re: Oil seals on Stihl MS660 keep going bad.
By: Al Smith Date: January 2, 2020, 7:43 am
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Just as a general statement often times the only sure way to
determine if a boot is torn is to remove it because often they
get torn on the bottom side .Which is often times caused by worn
out anti vibration mounts allowing the engine moving too much
within the suspension system .
#Post#: 85970--------------------------------------------------
Re: Oil seals on Stihl MS660 keep going bad.
By: Chainsawrepair Date: January 2, 2020, 8:42 am
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I've seen them torn under the clamp
#Post#: 85971--------------------------------------------------
Re: Oil seals on Stihl MS660 keep going bad.
By: emhusq66 Date: January 2, 2020, 5:06 pm
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Thanks Guys for your responses, i'm definatly going to check
impulse line, intake boot, and carberator. I will get back with
the results by monday, (I've got a busy weekend :o) I'll be in
touch and thanks again.
emhusq66
#Post#: 86126--------------------------------------------------
Re: Oil seals on Stihl MS660 keep going bad.
By: emhusq66 Date: January 24, 2020, 9:37 pm
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Hey guys, I figured i would finish this story so if anyone else
is having this problem maybe this will help. First I would like
to thank cut4fun and 3000fps, for their information they hit it
on the head, The culprit was the intake manifold with a 1/4"
slit on the bottom. The saw runs like a champ now , what a
beast! One more time, Thanks too cut4fun and 3000 fps for their
time and input, this site is is awesome. God Bless.
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