themaddhatter
ArboristSite Operative
Background:
Last week I was running my PS420. Earlier this year I swapped out the cat muffler for the non-cat factory one, and did a tach-based retune.
At that time, I set the RPM ~ 2,800 rpm, adjusted the low speed based on chainsawr instructions (turn CW until runs bad; CCW until runs bad; set in midpoint between two). I also set the high speed at 12,500 rpm. Used it off & on in the spring for short periods.
Last week, was limbing some blow downs, and it was running smokey at idle. Then, took a break (~ half tank left) & sat in the shade for a while to cool down (was in the upper 90s & high humidity). Came back, and had hard start. Usually when it is warm, you flip it on, one tug and off you go. Couple pulls and it wouldn't catch, so I set the throttle lock, gave it a couple pulls, and it would start on high, then die when the throttle was blipped. Didn't want to spend the rest of the time futzing with it, so I finished limbing with it's big brother (6401).
Did some research on AS, and went to the garage today to get it squared up:
- Pulled the plug, and one part of the plug was oily (telling me it was loading up correct?)
- Opened the muffler, and it was black sooty inside (again, loading up)
- Piston looked fine
- Changed air filter
- Changed plug
- Swapped out gas for fresh blended batch (91 no ETOH bought 3 weeks ago) with synthetic 2-stroke oil w/ stabilizer (50:1)
I had read comments from bsnelling about tuning in wood, and a comment from jus2fat on tuning more so by "feel". Following a hybrid of the two, here is what I did to the carb:
- Brought saw up to temp
- Found idle where saw seemed to run smooth w/ a tiny amount of chain creep (tach said ~ 2,700 rpm)
- Turned the low speed screw in quite a bit (about half turn) while checking throttle response (blip throttle). Found spot where saw didn't smoke & was not bogging on throttle blip.
- Mash the throttle, and it makes the "gravelly 4-stroke" coil limiting sound (at least as it sounds to me, as I have hearing issues)
- Buried in wood, was leaning it out, and it kept losing power. After futzing with it, decided to go richer than starting point. Noted power picking up. Kept going up to where the saw seemed to pull well (much better than earlier)
- Checking it with tach, saw hits ~ 12,600 unloaded; ~ 10,800 while pulling.
- Shut it down, easily restarts with 1 pull and idles well (tried several times after idle periods and WOT periods)
My questions are this:
-Does my carb adjustments seem reasonable? Or am I looking for trouble following the described practice?
-Dolmar specs idle @ 2,800 rpm. I am assuming me being at 2,700 isn't that big of deal, correct?
-Dolmar also specs 13,500 RPM for top RPM. With me being @ 12,600, should I be pushing to get that number closer? Would I just richen it up further?
-Does ~ 2,000 RPM drop in the wood seem right? I was letting the saw pull, not leaning on it, so it was doing the work on it's own.
Any feedback is appreciated.
Last week I was running my PS420. Earlier this year I swapped out the cat muffler for the non-cat factory one, and did a tach-based retune.
At that time, I set the RPM ~ 2,800 rpm, adjusted the low speed based on chainsawr instructions (turn CW until runs bad; CCW until runs bad; set in midpoint between two). I also set the high speed at 12,500 rpm. Used it off & on in the spring for short periods.
Last week, was limbing some blow downs, and it was running smokey at idle. Then, took a break (~ half tank left) & sat in the shade for a while to cool down (was in the upper 90s & high humidity). Came back, and had hard start. Usually when it is warm, you flip it on, one tug and off you go. Couple pulls and it wouldn't catch, so I set the throttle lock, gave it a couple pulls, and it would start on high, then die when the throttle was blipped. Didn't want to spend the rest of the time futzing with it, so I finished limbing with it's big brother (6401).
Did some research on AS, and went to the garage today to get it squared up:
- Pulled the plug, and one part of the plug was oily (telling me it was loading up correct?)
- Opened the muffler, and it was black sooty inside (again, loading up)
- Piston looked fine
- Changed air filter
- Changed plug
- Swapped out gas for fresh blended batch (91 no ETOH bought 3 weeks ago) with synthetic 2-stroke oil w/ stabilizer (50:1)
I had read comments from bsnelling about tuning in wood, and a comment from jus2fat on tuning more so by "feel". Following a hybrid of the two, here is what I did to the carb:
- Brought saw up to temp
- Found idle where saw seemed to run smooth w/ a tiny amount of chain creep (tach said ~ 2,700 rpm)
- Turned the low speed screw in quite a bit (about half turn) while checking throttle response (blip throttle). Found spot where saw didn't smoke & was not bogging on throttle blip.
- Mash the throttle, and it makes the "gravelly 4-stroke" coil limiting sound (at least as it sounds to me, as I have hearing issues)
- Buried in wood, was leaning it out, and it kept losing power. After futzing with it, decided to go richer than starting point. Noted power picking up. Kept going up to where the saw seemed to pull well (much better than earlier)
- Checking it with tach, saw hits ~ 12,600 unloaded; ~ 10,800 while pulling.
- Shut it down, easily restarts with 1 pull and idles well (tried several times after idle periods and WOT periods)
My questions are this:
-Does my carb adjustments seem reasonable? Or am I looking for trouble following the described practice?
-Dolmar specs idle @ 2,800 rpm. I am assuming me being at 2,700 isn't that big of deal, correct?
-Dolmar also specs 13,500 RPM for top RPM. With me being @ 12,600, should I be pushing to get that number closer? Would I just richen it up further?
-Does ~ 2,000 RPM drop in the wood seem right? I was letting the saw pull, not leaning on it, so it was doing the work on it's own.
Any feedback is appreciated.