Tuning the lo needle.

[2broke2ride]

This is a pretty basic question considering and it may have been covered but I can't find it. What is everyone's method for tuning the lo needle? I always seem to struggle here and all of the tuning info I can find always concentrates on the hi which I have no problem with.
I struggle with balancing my throttle opening and my mixture adjustment. Sometimes I get lucky and hit it right but more often than not I am messing with it through multiple tanks of fuel and maybe never getting it just right.

 

[Wood Doctor]

It varies from carb to carb, but I start with an average of 1-1/4 turns open and work from there. I just tuned a vintage Stihl 029 and 021 exactly this way after a carb rebuild. Both are running once again.

 

[ericm979]

Stihl workshop manuals have great instructions on carb tuning. While the specifics like default starting settings might be different the process will still apply.

The low mixture setting you end up with is a bit richer than the setting that results in fastest idle.

 

[lone wolf]

Set it to the stock setting and just tune it very slightly in or out till it holds idle nicely. Too lean will stall and too rich will blubber.

 

[heimannm]

With the saw thoroughly warmed up you should get crisp acceleration when you open the throttle. If you have to feather the throttle to get it up to speed the mixture is likely too lean, if there is a hesitation but the engine accelerates it is probably a bit to rich. You can often see a little excess smoke or even black smoke if the idle mixture is too rich.

A lean L will often give the appearance that the saw is "cold blooded" and will not accelerate nicely when you give it throttle.

A rich L has a fairly distinctive sound upon acceleration, sort of an audible "BWAAAW" when the throttle is opened.

Pick a saw that works as you expect it to, then experiment turning the L jet a 1/6th of a turn or so in either direction and you will pick up on the behaviors pretty quickly.

Mark

 

[Woodslasher]

I was told to lean it out until it stalled when you hit the trigger, then fatten it up until it accelerates crisply when cold.

 

[heimannm]

 

[Vintage Engine Repairs]

 

[Husky77]

This is a pretty basic question considering and it may have been covered but I can't find it. What is everyone's method for tuning the lo needle? I always seem to struggle here and all of the tuning info I can find always concentrates on the hi which I have no problem with.
I struggle with balancing my throttle opening and my mixture adjustment. Sometimes I get lucky and hit it right but more often than not I am messing with it through multiple tanks of fuel and maybe never getting it just right.

Remember one needle (H orL) will to a certain degree effect the other, find a video on adjusting the carb (something like tinman or ironhorse) when you get your ear in and understand what the engine is doing you will find it easy. Like anything you have to do it regularly to be proficient. The problem is if it's too lean on the L jet/needle it's hard to start and the same on the H will cost you a lot$$$ it may sound like it's faster but will go bang. Dont rush in, do your research and take your time, when you understand it you will notice the saw running much better and make it so much more fun, if you like hard work.