I believe that the default state for M-Tronic is lean (as in too lean to even run) as the EPA wouldn't want to allow the saw to run too rich with a malfunctioning system or cut solenoid wires. This sounds like the condition that you got. BTW, the M-tronic only controls the "H" carb circuit. The "L" and idle is controlled conventionally by just the carb. This would tell me that the solenoid is either clogged or not operating. To operate it needs power/pulse from the ignition computer/module.
The solenoid can be checked with a standard 9V battery after disconnecting the module. You should be able to hear it click.
@backhoelover mightr be able to set you up with some further M-tronic troubleshooting information.
Just a few things for clarification. M-Tronic controls
both high speed and low speed. There are 2 passages after the solenoid valve for the fuel. One is for the low and the other is for the high. The amount of fuel is given through the switching cycle, that the control unit gives to the solenid valve. Also it is very very rare that a solenoid clogs because of dirt. The fuel passages in the solenoid are bigger as the ones in the carburetor. In the past, but that is also very rare, there were the one or other solenoid valve stuck because of old hardenig rest of 2 cycle oil. But this can only be the case when a machine sits for a long time.
It`s right that the solenoid switch function can be checked with a 9V battery, but it is better
to not do that. In some cases it can fry up or destroy the control unit.
Also if you have disconnected the wires to the solenoid, or if there is a break in the wires, your saw will not run. In a condition like that you only get spark for a few seconds, because the control unit detects that there is no connection and shuts off the spark. The saw would also flood when there is no connection to the valve, because the valve is always open when unpowered.