Stihl KM110R Carburetor Adjustment

[henni]

Any recommendations on best steps for tuning carburetor ?
Found several excellent videos on valve adjustment and had no trouble performing same on this powerhead.
Did find generic Stihl Carburetor Adjustment.

In pictures below, see H, L and LA (Idle)

Online directions are like this:
How to Adjust the Carburetor on a Stihl Weed Eater

Turn the high-speed screw, marked 'H' counterclockwise until it stops.
Tighten the 'L' screw all the way, then turn it one turn counterclockwise to open it.
Start up the engine and allow it to warm up. The cutting tool will rotate. ...
Press the trigger of the machine to rev the engine. Adjust the 'H' screw until the engine does not cut out or sputter.

Heh .... someone just emailed this... a good one

 

[Kamele0N]

And where do you have a problem?

 

[henni]

Surprised the video had trimmer head attached but carburetor fully exposed (no cover, no filter).

 

[mk378]

I hope that Old Milwaukee is paying him.

Always tune with the string head installed and strings out at normal cutting length. The air filter doesn't make much difference unless it is clogged. You always want to be running a little on the rich side anyway.

 

[doitmyself]

Quote
Turn the high-speed screw, marked 'H' counterclockwise until it stops.
Tighten the 'L' screw all the way, then turn it one turn counterclockwise to open it.
Start up the engine and allow it to warm up. The cutting tool will rotate. ...
Press the trigger of the machine to rev the engine. Adjust the 'H' screw until the engine does not cut out or sputter.


The OP instructions don't make sense. Here's the owner's manual version: https://www.stihlusa.com/webcontent.../stihl_km-110-130_instruction-manual.pdf ... see page 20.

Initial adjustment before tweaking:
"- Carefully turn both adjusting screws counterclockwise as far as stop:
- The high speed screw (H) is 3/4 turn open.
-The low speed screw (L) is 3/4 turn open.
- Start and warm up the engine.
-Adjust idle speed with the idle speed screw (LA) so that the cutting attachment does not move."

Think of it this way: The L screw (needle) adjusts the fuel/air mixture at idle and early/low throttle engagement. As the throttle opens more, the H screw (needle) takes over and adjusts the fuel/air mix for wide open throttle. If you have poor acceleration/sputter when pulling the throttle quickly at idle, you adjust the L screw (not the H in the OP). The LA screw adjusts the idle speed. When you adjust the H or L screws, you may need to tweek the LA screw and vice versa.

On chainsaws you adjust the H screw open (rich) until the engine starts to "flutter" under no load. Under load that flutter will settle into smooth, high power cutting. I'm not sure about tweaking a weed trimmer H screw beyond the stated 3/4 -1 turn out from closed.