Help with tuning MS 661 carbureted model

[Stihldobie]

Hello All,
I have a 2022 MS 661 carbureted model. I recently modded it with a West Coast Saw Bark Box. I have run several gallons of Husky premix. Saw has never seen ethanol. Currently I am at 2.75 turns on the L and 2.25 on the H. Plug is still very white. The limiters are removed so these settings are from needle seat to aforementioned position. Saw seems to run ok, but does fluctuate rpm in the cut. If I go further out on the H, rpm seems to drop off as would be expected. No matter what I do, the plug remains mostly white. Either way, the needle screws don’t seem to respond like I am used to. Anyone have any thoughts on this?

 

[Mad3400]

Assuming the powerhead is in good working order with no issues, just keep turning the High jet "Out" in increments until the plug or exhaust screen turns your desired shade of brown.

A Tachometer is also a worthy investment.


Mad3400

 

[Stihldobie]

Assuming the powerhead is in good working order with no issues, just keep turning the High jet "Out" in increments until the plug or exhaust screen turns your desired shade of brown.

A Tachometer is also a worthy investment.


Mad3400

Assuming the powerhead is in good working order with no issues, just keep turning the High jet "Out" in increments until the plug or exhaust screen turns your desired shade of brown.

A Tachometer is also a worthy investment.


Mad3400

Yes, power head is mint. Low hour saw. Turning out the high jet will richen it up and knock down rpm and performance, but even keeping it rich enough to do this will not make that plug anything but white. And it starts sounding really weak and ratty.

 

[Mad3400]

They aren't like the older saws where you turn them pack 1 to 1 1/2.

I believe in my case, after removing the limiter caps, it was 3 to 3 1/2 turns.

Maybe there's little bits of debris clogging the jets just enough to be a pain?


Mad3400

 

[stihltech]

Stihl shop manual states 1 turn on low side and 1 1/2 turns on high side. You need to look for vacuum/pressure leak. Also check the fuel supply side.. Don't forget the vent. Definitely too lean somewhere.