I'm not sure how long they ran their saws on each octane before cutting. Do we know what "long enough" is?
This is the recalibration procedure as far as I know.
1. With the chain brake engaged…
a. Hold throttle and set start lever to Start position (Δ)
b. Start saw and let idle in Start position (Δ) for 90 seconds
c. Blip throttle to bring the machine to the Run position (I)
d. Immediately move lever to Stop position (O)
e. This will reset the carb to original factory setting.
2. With the chain brake engaged…
a. Hold throttle and set start lever to Start position (Δ)
b. Start saw then Blip throttle to bring the machine to the Run position (I)
c. Let idle in Run position (I) for 90 seconds
d. Immediately move lever to Stop position (O)
e. This will calibrate the idling characteristics of the saw.
3. With the chain brake engaged…
a. Hold throttle and set start lever to Start position (Δ)
b. Start saw then Blip throttle to bring the machine to the Run position (I)
c. Disengage chain brake and make five uniform cuts through a minimum 12-inch-diameter log.
d. This will calibrate the full throttle characteristics of the saw.