28mm vents

I'm running some 28mm carbs on my kz1000.Theres 2 vents ports on them.Im running a rubber type 900 air box instead of the hard plastic original box.If I plug the vents,the bike runs like crap.I feel like I'm sucking dirty air in.My engine is 1075 with 425 lift cams,& z1r valves.Maybe I need bigger carbs anyway.I think these carbs were from an early 900.Any help is apreciated.

The vent tubes on the Mikuni carbs are not used to suck in any air. They allow air to escape the carb bowls as the bowls fill with fuel. The tubes are intended to exit into the open air. The ends on the ones on my KZ650 drop down into the top of the air filter so any fumes from the carb bowls are sucked into the engine. The air baffle on mine is shaped at the bottom to hold them in place. Ed

Even the tool bag and the rubber hold down look brand new on Eds bike.

Good info.I thought since it ran like crap when I plugged them,then they must be sucking air.I'll run me a couple hoses into the top off box.