Chainsaw Repair

Picked up a ms261c the other day and pulled the carb (C1Q s229) off to get an idea of how the fuel is being metered.  Thought it had a Throttle position sensor but the position sensor is hooked up to the choke shaft. There is a small electronic metering device the us fe via two feeder holes under the metering diaphragm. Looks like the metering unit regulates high speed and low speed, although there is a fixed brass inlet orifice leading from the metering unit to the low speed Welch cavity.  I'll put a multimeter on the choke shaft position sensor and check if its varying current to the fuel regulator or if it's simply an on/off swith for the metering unit. 

Anyone else get a grasp on this carb yet? Seems pretty simple so far