The chain is already spinning...

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1750

Minister of Fire
Apr 21, 2013
532
Michigan
I cut all day with my little Stihl MS-170 yesterday. That saw is a trooper!

Sometimes I noticed that when I started it up, the chain would start spinning as soon as I took the brake off and before giving it the gas. Similarly, after finishing a cut sometimes it keeps spinning (and fast) even when I'm not pulling the trigger.

I've taken it apart and cleaned everything up. It doesn't seem to be a sticky trigger assembly, because it happens even before it's been given the gas. It doesn't happen even most of the time, but I'd like it to happen none of the time as I could see it creating a dangerous situation.

If anyone is familiar with this problem and has suggestions for fixing it, I'd appreciate your input.

Thanks!
 
Just to cover all bases, are you familiar with Stihl startup procedure? The "Warm Idle" position is actually a "fast idle," which will cause the chain to spin rapidly.

Chain spinning at idle could mean the idle setting (LA) on the carburetor is too high. However, this usually is a little movement and not spinning rapidly.

Clutch springs may need to be replaced.
 
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Yes, I'm familiar with the start-up procedure. Although, now that I think of it, the saw stopped doing it as much after I'd been cutting for a while and could just start from the first position. I've got a bit more to do today to finish up. I'll go pay better attention to where the control lever is.

When I start I typically have the brake on. After it's up and running, I drop the brake and that's when it starts spinning.

Regardless, thanks for your reply. I'll go pay a little better attention to what's going on.
 
could be lean on the idle screw too
 
Thanks, Bob.

I just went out and finished cutting up the smaller stuff. There wasn't any problem today, so maybe it was just me messing something up.

Thanks again.
 
My 290 did that almost since it was new. It was my first Stihl so I just got used to it. I tried tightening the chain and lowering the idle speed to get it to stop.

It finally drove me nuts so after removing the sidecover, bar, and chain, I popped off that e-clip and pulled the sprocket/clutch drum off. This is all really easy. I was happy to find that one of the clutch springs was broken. Replaced the pair of springs for super cheap and put it back together. Totally different saw.

It's not a pro model but when the chain is sharp, that saw can make some firewood fast.
 
Does it have the auto-tune carb? My 180 does and it also spins occasionally, but just as its getting warmed up. Once it's warm there's no problem.
 
My 290 did that almost since it was new. It was my first Stihl so I just got used to it. I tried tightening the chain and lowering the idle speed to get it to stop.

It finally drove me nuts so after removing the sidecover, bar, and chain, I popped off that e-clip and pulled the sprocket/clutch drum off. This is all really easy. I was happy to find that one of the clutch springs was broken. Replaced the pair of springs for super cheap and put it back together. Totally different saw.

It's not a pro model but when the chain is sharp, that saw can make some firewood fast.

Thanks, HB. The problem is variable, so I don't think anything is broken -- sticky, maybe, but not broken.

This saw has a lot of heart. It's a 16" bar working through 18" of sugar maple all day long. I had never had it do anything but smaller diameter stuff, and was impressed with what it could do.

Thanks for your reply.
Does it have the auto-tune carb? My 180 does and it also spins occasionally, but just as its getting warmed up. Once it's warm there's no problem.
Jeff, I don't know if it has an auto-tune carb. Your description fits what I experienced, though. As soon as it was warmed up things seemed to be fine. I'm cutting against next weekend, so we'll see if the pattern repeats.

Thanks to you both.
 
This is an intellicarb model.....
 
Intellicarb sounds like something from Star Trek, Bob.

I could only hope to have an Intellicarb! :)
 
Well you didnt say how old it was........ Check your filter and low speed fuel screw, as long as your clutch is functioning properly. A hole in your filter can cause this too
 
Thanks, Bob. I don't actually know how old it is. It came out of someone's garage as part of an estate.

I've got a pdf of the manual, I'll have to take a closer look.

Thanks!
 
Engaging the chain brake while not actively cutting is standard practice recommended by every entity that promotes chainsaw safety. I don't do it but it is the standard.

Yep, I took a Game of Logging workshop this past Spring and two of the safety violations for which they deduct points are starting the saw or taking more than 2 steps with the brake disengaged.
 
I don't argue those points but every saw manual I have seen states that at idle the chain should not turning,.......
 
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Engaging chain break between cuts or while walking prevents incidents resulting from inadvertently hitting the throttle trigger. The problem presented in this discussion has the chain moving without hitting the throttle trigger. If chain is moving at idle, something needs to be corrected.
 
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When you take the chain brake off are you pulling the throttle at the same time? ..... Really?
 
I think it's a stupid rule that the chain brake ever be engaged as a matter of SOP. The chain should not spin at idle regardless of the existence of a chain brake.
 
I never use my brake.

If your saw is working right, the chain won't be turning when you're not pulling the trigger, and you can't pull the trigger without your hand fully around the trigger handle to first push down the trigger release thingy.
 
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