hvdm wrote: ... So how do I secure it once I've mounted it to the carbs? Just tiewrap it into place ?
On Z1's there's a forked bracket bolted to the bottom of the battery box that supports the weight of the airbox assy. at the rear. The forked end of the bracket straddles the filter cavity drain, which is the short, hard nipple directly below the air filter, not the nipple for the rubber elbow at the bottom of the plenum.
Left unsupported, the weight of the rack of carbs, airbox & filter assys. bouncing when the bike is in motion stresses the carb boots, mostly downward, hastening splits developing across the top of the carb boots as everything rearward tends to sag.
We're unfamiliar with the chassis/battery box configuration of KZ900's in the airbox area. If existing bracketry does not lend itself to supporting the weight at the rear of a Z1 airbox when installed in a KZ900 frame, we'd suggest tie wraps or other means of support.
Good Ridin'
slmjim & Z1BEBE