Need some guidance tuning a Stihl

[boda65]

I need a little guidance. I sharpen a couple saws for an older friend of mine. He is not a chainsaw fanatic, just a homeowner with a couple saws for grounds upkeep. He mentioned that this 025 of his runs and cuts great, but won't idle, so I said I'd look at it.
Here's where I get lost. I mostly dabble in vintage saws. The tuning consists of high, low, and idle speed. This saw has L and LA. Yes, I realize I live in the dark ages and probably every saw made in the last 20 or 30 years is like this, but I do not have experience with it. Could someone give me a brief overview of tuning this saw? I did search this site, and came up with a lot of high speed tuning info, but I am having problems with idle.
On a side note, this saw has what looks like a piece of tubing coming up from the fuel tank with a couple of set screws in it? WTH is that? Here is a pic of it. The HO doesn't mess with his saws, so I'm guessing it came that way.

Thanks in advance for any help.

 

[blsnelling]

Those are grub screw, which are your tank vent. There is no H adjustment on that carb. All you can do is adjust for best idle and throttle response with the L. LA simply sets the idle speed.

 

[boda65]

Thanks, Brad

 

[heimannm]

Brad has given you good advice as usual.

While you are in there, have a look at the fuel line and impulse line. Someone brought a new looking little Stihl saw to me last year to try and help them diagnose a hard starting problem. The fuel line looks like it was made from aligator hide...

Mark

 

[brages]

"Won't idle" is frequently a gummed-up idle circuit in the carb...

 

[JustinM]

You got the perfect advice so far.

I'll second the part about the fuel line though.

Since this is a only partially adjustable carb, if you cant get a satisfactory result with idle, its possible you need to check the fuel line & gaskets on the carb itself. The other thing to look at is the muffler. My dad has a non adjustable carb on his ms180 and it wouldnt idle properly. I tried tweaking it a bit but to no avail. I pulled the muffler & sure enough there was a decent amount of carbon build up on the the screen. Once i gave it a good clean the thing idled like brand new.

Good luck!