So I recently acquired a 96 900rr as a project. While taking off the gas tank I got a bit of a surprise: a gravity-fed petcock (I think? I'm not very motorcycle-literate, but browsing the forums I assume that the 96-99 petcocks are vacuum, and pre-96 are gravity).
So when I removed the tank the only line I removed was the fuel line. As in the picture, the drain tube is capped (as in the picture) and the breather tube (the other nub next to the drain tube?) was disconnected. Brief note: the bike was able to start up and run fine previous to me taking it apart.
So now I have the following questions:
1) Did I correctly identify the breather tube? If so, where do the connections run? I have the following image:
Does the curved part connect to the breather nub while the two others vent to free air?
The 90 degree line goes to the small nipple under the tank. Pretty sure that's the breather for the tank. If it were capped you would have running troubles. But a tough look at the nipple seems like it might already be clogged. The T section tucks into the frame there as in your pic, and the longer line just runs down the frame to atmosphere (open).
2) Do I need to do anything for where the vacuum line is supposed to connect on a 1996 fuel valve? I was reading the following post:
Do I need to cap the nub coming of the right side of the carb? I'm assuming that's where the vacuum line is supposed to feed per the link above, but my bike has no hose there (just the nub).
The nub you speak of is actually a brass port or nipple coming off the cylinder head. On the SC33 engine (96-99) it is a dedicated cast port under the #2 intake tract on the head itself, not the carb. If you are going to continue to use your current set up make sure it is capped. Otherwise it's sucking in unfiltered air.
3) Whats the purpose of the fuel tank drain tube? In all the diagrams I find, there's a hose that runs from the drain tube down the Left side of the bike. Is it supposed to normally open to air? Is my current set-up okay or should I find a hose and throw it on?
Sometimes the steel "lines" inside the tank rust out or become clogged. If they rust out then the fuel inside the tank leaks down and out the nipples. Probably why the drain is capped. That normally will also have a hose on it to direct gas and or water etc that collects under the rim of the gas cap and around the filler mouth. It just directs it to the ground via the hose. I guess you could uncap it and see what level the tank needs to leak out of it.