Post muffler mod tuning

[Chris-PA]

glad to hear you got the problem fixed.



agree!!

don't have a stihl, but the walbro carb on my husqvarna has an air bleed. air bleeds, just adjust the point where idle/main transition take place is all i know. this is based on air velocity. air flow is a relative term i guess, based on total volume.

is the richer (fuel) adjustment necessary based on?
a. air velocity
b. air flow (volume)
c. the altering (opening up) of the muffler which lessens the 'supercharging' effect of the back-wave as shown at the bottom of page here:

2 STROKE Guide to Wisdom

i say "c".....and a very sharp chain.

-OMB

The only Walbro I've seen with an air bleed so far is the WB. And yes, airflow is poor terminology for air velocity, which was in the wiki quote I listed above. You really have a pipe like that on your saw?

 

[madpogue]

Problem fixed

What was it?

 

[dallypost]

What was it?

Just terribly flooded. Got it dried out, tuned it, cut a bunch of wood. Everything is good again.

 

[one.man.band]

The only Walbro I've seen with an air bleed so far is the WB. And yes, airflow is poor terminology for air velocity, which was in the wiki quote I listed above. You really have a pipe like that on your saw?

agree an actual 'air bleed' passage to the main jet in a small diaphragm carb is a rare thing. what 'i' call an air bleed is a hole or notch in the throttle plate itself, which acts like an air bleed. adjusting the hole size larger or adding another would keep the idle circuit going longer from off idle (part throttle). or notching (filing) the throttle plate just over the idle progression holes could be done. enlarging the idle progression hole closest to the main jet would also add to this effect.

don't know why all this would be necessary on a chainsaw though, unless it needs better idle adjustment than what the factory provides due to mods and such. (just my opinion, for what it's worth). if it was a chainsaw powered skateboard or something that needed part throttle, then maybe so.

looking closer at my husqvarna, it has a dang zama carb. oh well, it works good.

i do not have a 'pipe' on my saw. but all 2 strokes, even with a box shape muffler reflect a back wave, (probably not at the right timing though), like the animation does. think the raw and burnt gases still bounce back and get re-burned a couple of times as well.

-omb

 

[ri chevy]

Muffler mod and carb tuning

opcorn:

There are a few threads already on this with the 029/290.

http://www.arboristsite.com/chainsaw/66105.htm

Glad to hear that your saw is OK and you got the issues fixed.

 

[Chris-PA]

agree an actual 'air bleed' passage to the main jet in a small diaphragm carb is a rare thing. what 'i' call an air bleed is a hole or notch in the throttle plate itself, which acts like an air bleed. adjusting the hole size larger or adding another would keep the idle circuit going longer from off idle (part throttle). or notching (filing) the throttle plate just over the idle progression holes could be done. enlarging the idle progression hole closest to the main jet would also add to this effect.

That's not at all the same thing, it just adjusts the position of the throttle plate relative to the idle and idle transfer ports.