similar problem here as well on mc18 r2k,

when i turn the servo manually with the ignition is off and switch it back on, it sets to the low position. and when i start it and rev the bike it tries to turns past the low position and hits the stop when it should be moving towards the hi position. i have changed the servo, servo control unit and cdi. the only unit/box that i have not changed is on the opposite side to the cdi unit, it also plugs into the servo control unit.

it could be that unit that is broken but i dont know what it is?
i couldnt find it on my wiring diagram.