Confused, how do I know which version, MS 261 C that I bought?

I am not aware of any design changes in the 261cm.

 

I have the CM261C-M since there are no holes to use a screw driver to adjust the Carb. it has to be this one i called Stihl Tech. Support today about.

The MS261C M has the M-Tronic feature, which is an electronic fuel management system. The engine has several sensors which measure temperature, barometric pressure, air flow through the air filter, and fuel flow. These sensors send information to a control unit (Normally called an ignition module or “coil”, which then sends adjustment commands to the solenoid attached to the carburetor, which then makes adjustments to the carburetor at the rate of 30 TPS.
Thank you again for your email.
Best regards,
Wayne Lemmond
Technical Service Representative
STIHL Inc.

I also have read about this calibration you need to do, i have just started my saw and run it, i don't see anything needed as it runs just fine, maybe i am missing something but until it won't start or runs poorly i will just not worry about any calibration .

 

After further research, seems like the newest 2020 261/261c's have not only the v3.0 mtronics but a different piston. Idk, I think all versions of the 261/261c are fine saws FWIW. Not sure when they started shipping these exactly. On another note, after further investigations on other forums and what not, doing a "reset" on a mtronic OR autotune saw just for the sake of doing it is not advised. Husky autotune needs to be plugged into a computer for this, whereas the user can reset a mtronic without having this.... If your mtronic or autotune is performing good then leave it alone in other words is what I gathered from many a chainsaw people I respect. Cheers.

 

Off Topic , but Something I’ve noticed ( or maybe imagined ) with AT ,and probably MT saws ...
Don’t do a lot of needless pizz reving them . They tend to start richening themselves . I think it’s a reaction to keep the saw from pegging off the rev limiter .

 

Agreed, a coworker of mine had a chain jump on a non m 261. He slapped the chain back on and pizz revved and kept it pinned. I could hear it was lean and screamed at him, but it was too late.

 

same here. I know the 261C will have that on the pull rope cover and the carb version just "261".
If it works okay just go with it. Ask the OPE dealer next time your in there.