xz400/550 was a pain in the arse, carbs were twin downdraft with accelerator pumps & hoses going everywhere. Were carb mods & airbox p**s flap updates early on. Flap was controlled by a vacuum diaphragm thingy that controlled the air at the airbox entry by memory. Reminds me--had one at work that someone had put sealer stuff in the tank & fueled it up too early no doubt, then this bloody cat piss smelling glue went through pretty much everywhere it could get in the carbs. The 550 was raced in the 6 hour over here [nz] but remember constant fiddling during the practice days before then think big ends the night before--not sure if it saw the 6th hour in the end. Steered weird too but probably 'mind over matter' because they look 'wrong'. Had a lot of offset [step forward] on the yokes so everything theoretically worked out with sliders reversed but i could never see the point in it apart from a gimmick [yamaha trickery]. Sorry getting off subject--what was it again!!].