Breather on GSXR tank

[STM77]

Hi all, been a forum member for a little while and have a question. In the process of trying to work out the tank on my 89 GSXR for my build and am stumped. Can the breather or vent on the top of the fuel tank in the early(89) GSXR be sealed up? Does the fuel cap need to be replaced with a vented one if it is. I've seen some of the other bikes on the forum and some seem to have them sealed and some don't. Cheers

[evilkarl]

If your fuel cap seals tight, and the breather hose sealed, you won't get any fuel, its needs a breather somewhere above the fuel level. Same theory as holding your finger over the top end of a straw full of liquid.

[chopaweeza]

You need a vent. As the early GSXR types are proper Aircraft Fillers(proper ones don't have a breather) you need to modify the cap if you are going to run it without a breather. Modifying it can be a bit fiddly but generally I wouldn't advise doing it. Where the breather is on the stock tank allows the full capacity of the tank to be utilised. When you modify the cap to vent it lowers the level of fuel you can safely put in the tank without having fuel piss out the vent after filling up. Saw a nice paintjob ruined on a modified slabby because the owner have the top smoothed down with the vent removed & the cap drilled to vent it. The tricky way to do it is to braze or weld thin tubing into the tank that exits the underside and rests just under the top of the tank. Some stock jap tanks already do this and you see a similar arrangement used for the overflow on some recessed . Bit tricky to do but makes for a cleaner look. I did similar on a chopper tank that used a proper aircraft filler and the underslung breather pipe looked just like an overflow .

[STM77]

thanks for the input fellas. Helps clear a few things up.