Fuel Tank Vacuum?


Sorry if this sounds dumb, but when I open my fuel tank after riding, I have to pry it open, which releases what appears to be vacuum pressure inside the tank. You can actually see the top of the tank move up a little once the vacuum is released. :super:

That just doesn't seem right...
I believe it has a vent line that keeps a vacuum from forming, maybe it is clogged or a bug got in it? If it is developing a vacuum it may be starving for fuel as well, due to the added resistance inside the tank in being able to draw fuel out through the pump. I think I remember reading in the Busa manual that the tank breather lines come out in the area of the foot brake or maybe below it and had two lines tied together. If i'm right, hope this helps!
raise your tank, and while raising it, check all the fuel lines.. one must be kninked. as you know this can also result in driveability issues.... it happens sometimes during assembly - crimped/kinked fuel line.
Well, I raised the tank, and sure enough, the vent hoses at the very back of the tank under the seat were pulled tight straight down thru their clamps, completely kinked. :mad:

I pulled them off and clipped a little off the ends to get rid of the kinked part, pulled a little slack up from below, and put them back on. No more kink. Thanks a bunch Justin and cache :beerchug:
No problem ICW! Glad you got the problem fixed. I guess it pays to endlessly thumb through the service manual, well maybe not endlessly. :D
There were problems with some Yamaha's cruiser bike's gas cap check valve sticking. The vacuum would collapse the tank and ruin it.