The Honda 500K & 550 family bikes went through an engine size change as well as a different model carburetor used on the CB550K3 & 4. Here are the jet sizes to the best of our knowledge. We have seen combinations of following:
CB500K
Main Jet Primary (Needle Jet): #100
Idle Jet (Pilot Jet): #38
CB550K & F
Main Jet Primary (Needle Jet): #98
Idle Jet (Pilot Jet): #38
CB550K3 - K4
Main Jet Primary (Needle Jet): #90
Idle Jet (Pilot Jet): NON REMOVEABLE