What is the spec. for air pressure on the front fork of 2000 royal star?

It it's a Venture, there's a knob on the left side, in front of the fork pivot, turn clockwise to lower the beam, counterclockwise to raise it.

If it's just a Royal Star, the adjustments may be made through holes on both sides, cut low in the headlight rim.

Head bolt torque is 32 ft.-lb. (43 nm)
Head cover bolt torque is 7 ft.-lb. (10 nm)

you have to take the forks off and put the tubes on v blocks.. and with a dial indicator check the specs

There are no preload, compression or rebound adjustments on either end of a 1996 Royal Star. The front fork characteristics can be changed by internal modifications to the front fork piston and a change in fork oil weight (stock is 5W), lengthening the spacers immediately beneath the cap bolt, or addition of progressive springs. The rear shock absorber assembly is a unit with no serviceable parts, no modifications are practical. The only aftermarket suspension parts I've found for the 1996-1998 Royal Stars are kits offered by Hyperpro (ECM), they list kits for the front forks SP-YA13-SSA05 and the rear SP-YA13-SSB05; however, since the rear kit is purported to fit all years from 1996 to the present, and the rear suspension was redesigned for the 2002 model year, I suspect that you may find that the rear kit doesn't work at all.