Complexities of Throttle/Low Circuit

[maowwg]

So I have a couple question. Repaired a friends Craftsman pre-strato square box top cover with the ridge for the spark plugs Anti Vibe chainsaw. It’s the sister to the Poulan 2550. I think it’s a Type 6 or Type 7?

So new lines, clean carb, needle valve clicking with the new metering diaphragm being pushed up and down , refueled and reassembled.

So I go to adjust the carb snd set the idle nice snd slow. With the low screw 1.5 turns the saw bogs when the trigger is pulls and between 1/12 and 1 3/4 it loads up and pukes before it achieves the quick snappy trigger response. At 1 3/4 the saw has great trigger response but the idle has to be turned in to keep it from loading up so is not a bobble bobble bobble. It’s a running motor. Chain is not moving, so it works but it’s a faster idle.
First question, is there anything I missed? It’s running snd completely usable, as it is, but the idle is kinda fast to keep it from puking with the low set to the richness it needs to accelerate
Question two, should the idle be set to just short of chain engagement or is or better to slowly bobble?
Third question, is this even a concern or should I get a life and not worry?

 

[Old2stroke]

Many saws, especially small ones have to have the idle speed set high to get a consistent idle that will run without stalling, if this can be achieved at a speed just below the point where the chain moves, forget what it sounds like, you are good to go.

 

[ironman_gq]

Most saws idle around 2800rpm, basically they want to idle as high as they can without the chain moving.

 

[maowwg]

So is that the sum total of it? Run the idle to the brink of the chain moving, back it down and don’t worry about the low circuit as long as you get trigger response? Where along the continuum of low circuit richness do you get the best cold start and hot restart reliability? As rich as she will go with a fast idle OR something less than that toward the lean side of the snappy trigger response zone? Or again doesn’t it matter?

 

[Old2stroke]

Cold start has little to do with the idle mixture, it is more about how effective the choke is and whether or not the operator knows how to advance the throttle for the right starting procedure. Generally the best idle is achieved by adjusting the L mixture when the saw is hot and "most" saws will be happy with the leanest setting that will still give snappy acceleration. If you want the saw to start when hot without touching the throttle, the more open the throttle is at idle, the better it will work and if it won't do this, it might mean you will have to set the idle speed higher (more throttle opening) with the chain just moving and then back out the L screw until the engine slows down enough to stop the chain but there are limits to what you can do without getting the idle so rich that it won't hold a consistent speed. If a hot saw won't start with a couple of pulls without touching the throttle, you have to set the carb to the fast idle position or you could be pulling for a long time.