STIHL 066 chain running out of control while idling

[Stihl dude]

Hello all

I have a STIHL 066 that just got out of the shop and mechanic said it was “tuned” right.
The saw has aftermarket exhaust on it. Throttle response is good and engine seems to be running good.
while idling, the chain keeps turning and sometimes turns at high speed. Any idea on what could cause it? clutch springs? (Using Stihl premix)
Check video below

 

[trains]

Just watched the vid, its sounds on the lean side to me at both idle and coming down off wide open throttle.

usual disclaimers apply for internet diagnosis tho.

I know nothing of what type of service was done to it, nor any repairs etc and what parts were replaced during said service.
Nor how they went about tuning it either.

Are you comfortable tuning a saw/ 2 stroke equipment, what is your level of experience, do you have a tach to read rpm etc ?

Possible causes of chain running at idle are.

idle speed too high, clutch engages at 3600rpm if springs are ok.

Build up of crud/ saw dust/ oil on the clutch drum rim, dragging on the clutch shoes.

Too much grease on the clutch drum bearing, causing it to drag.
Not enough grease, and a dry bearing on the clutch drum bearing causing it to drag.
physical damage to clutch springs and causing drag.

so you get the idea.

Now possible reasons for the idle too high
could be
set too lean on the L needle, richen 1/8 to 1/4 of a turn to get a more burbly idle, and idle speed will drop as well.
If you go too rich on the L, it will stumble at idle, load up and then eventually stall after 20-30 seconds of idling.

Air leak from any of the fuel hose, impulse hose, intake boot, and crank seals.
press/ vac test and visual inspection will diagnose those.


so you can see it could be just an easy re adjustment to richen it up a bit, and lower the idle speed to below where the clutch shoes engage, or it could be that and worn spring or many other things.
Also, there is a set way of setting your base idle and L, and LA settings, if they are not done correctly, you can easily chase your tail on idle setup.


So

Richen the L 1/8 to 1/4 of a turn, take notice where the setting of the needle is at the moment if you want to put it back to that setting, and then let us know how it sounds and behaves like that, post up another vid, and we can step thru it from there, no point in leap frogging over an issue, lets methodically step by step so you find and fix the problem.

cheers


Edited to add the vid.
can give you an idea of how it should sound as the mixtures change.

 

[Stihl dude]

Just watched the vid, its sounds on the lean side to me at both idle and coming down off wide open throttle.

usual disclaimers apply for internet diagnosis tho.

I know nothing of what type of service was done to it, nor any repairs etc and what parts were replaced during said service.
Nor how they went about tuning it either.

Are you comfortable tuning a saw/ 2 stroke equipment, what is your level of experience, do you have a tach to read rpm etc ?

Possible causes of chain running at idle are.

idle speed too high, clutch engages at 3600rpm if springs are ok.

Build up of crud/ saw dust/ oil on the clutch drum rim, dragging on the clutch shoes.

Too much grease on the clutch drum bearing, causing it to drag.
Not enough grease, and a dry bearing on the clutch drum bearing causing it to drag.
physical damage to clutch springs and causing drag.

so you get the idea.

Now possible reasons for the idle too high
could be
set too lean on the L needle, richen 1/8 to 1/4 of a turn to get a more burbly idle, and idle speed will drop as well.
If you go too rich on the L, it will stumble at idle, load up and then eventually stall after 20-30 seconds of idling.

Air leak from any of the fuel hose, impulse hose, intake boot, and crank seals.
press/ vac test and visual inspection will diagnose those.


so you can see it could be just an easy re adjustment to richen it up a bit, and lower the idle speed to below where the clutch shoes engage, or it could be that and worn spring or many other things.
Also, there is a set way of setting your base idle and L, and LA settings, if they are not done correctly, you can easily chase your tail on idle setup.


So

Richen the L 1/8 to 1/4 of a turn, take notice where the setting of the needle is at the moment if you want to put it back to that setting, and then let us know how it sounds and behaves like that, post up another vid, and we can step thru it from there, no point in leap frogging over an issue, lets methodically step by step so you find and fix the problem.

cheers


Edited to add the vid.
can give you an idea of how it should sound as the mixtures change.

WOW! HAHa wasn't expecting such a detailed response.Thabk you very much it helps a lot.
Just ordered a digital tachometer and new clutch springs. Should come in tomorrow.
I will post another vid tomorrow afternoon

Thx again!!

 

[stihltech]

Does the chain turn when cranking before startup?

 

[Stihl dude]

Does the chain turn when cranking before startup?

If the chain brake is not engaged, it does turn.

Is it an issue?

 

[Woodslasher]

It just means the problem (at least partially) lies in the clutch/drum end of things. The chain shouldn't spin when you pull the saw over, unless a clutch shoe is dragging or the bearing isn't spinning.

 

[Charlie Coyote]

It just means the problem (at least partially) lies in the clutch/drum end of things. The chain shouldn't spin when you pull the saw over, unless a clutch shoe is dragging or the bearing isn't spinning.

Or more likely that he needs to learn how to tune the carburetor

 

[stihltech]

Take it apart and look!