I assume the bed is filled so you can't carry it there? That rack should work fine. My only concern would be how much weight the bed is already carrying before you throw another 400+lb pendulum/lever on the back.
FWIW you want more than 10% of the total weight of a loaded trailer on the tongue, but less than 15%. In your case with a full bed and 400lbs on the tongue weight you're going to be sagging and be a ton rear heavy going around corners.
The channel for the bike is 71" long, figure you'll lose 13" from the front of the tire to the axle which leaves 58" of wheelbase left to set the bike on. The CB750 has a 57"+ wheelbase. It will barely fit. Not the way I would want to haul a big bike. That rack is for dirt bikes. Long tongue arm will have the bike more than 2' off the rear enhancing the leverage and tongue weight.