Even with the tappet adjusters completely backed off, the rocker arm paddles will hit the cam lobe. You can pinch #1 intake rocker between your fingertips and feel it rise and fall as you spin the engine. Spin the engine until you feel #1 intake begin to rise, then look at your timing marks and spin the engine to 1-4 "T" mark. You are now on compression stroke for #1 cylinder and can set gaps for..
#1 intake and exhaust
#2 exhaust
#3 intake
Spin engine 360 degrees(one revolutuion, returning to the 1-4 "T") and set gaps for..
#2 intake
#3 exhaust
#4 intake and exhaust
DISCLAIMER: I may have the specs for #'s 2&3 cylinders reversed. Please consult your manual before proceeding as I am just going from memory. Process described is for a CB750