Mamba monster wont except sync -reverse

[suicideneil]

I have a DX6i & MMM too. When I installed mine, I used an rx battery pack to power the rx in order to bind it to the tx, then plugged the esc into the rx to calibrate it. Providing your epa and throttle travel etc are all at default settings you shouldnt have any issues calibrating it:

power up the esc & rx
pull full throttle
turn on the tx
wait for beeps/ leds to change
pull full brake
wait for the beeps/ leds to change again
release to neutral
the MMM should beep the full arming tone indicating its calibrated.

Only possible problem really is that the arming time is quite short on the MMM as standard, so use the castlelink to raise it to 2-3 seconds and try again.