Black Magic Racing took a look at the T-660 Turbo models and found that these sleds are not immune to engine movement. You wouldn’t think that a motor that big would even need to be bolted down! Oh yea, she moves.
They got a good feel of how the motor was moving, just like any other sled, up and back, basically trying to twist itself out of the chassis. This, as you may already know, really screws with the efficiency of the clutches, is hard on belts, and hard on the mounts and everything else that is attached. They quickly designed a torque arm, installed it where they believed it would be the most effective, and wham, engine movement was nearly eliminated.
In a nutshell, the 660cc 4-strokes are no different than the 2-strokes, they move too. If you need a torque arm, contact Black Magic Racing and ask for part number 70-1471 for $59.95.