Join Date: Feb 2008
Motorcycle: GSX-R750H, Ducati 1198 SP
Re: '87 GSXR 750 fuel line routes
#1 and #2 are for the air vent pipes that originally routed along the airbox, (1 on each side) down and back toward the swingarm pivot to open air.
#3 is the main fuel line going from the fuel cock to the carbs.
What's missing is #4 (fuel cock vacuum line) which connects to the fitting above #3 (on the same carb) up to the fuel cock.
Hope this makes sense.