Hi Vacuum in fuel tank

Howdee...I have a 08 X Cali model with Power Commander FMF Q4 and airbox flapper mod.....have about 10K mi on the bike and this is the first time it acted up....rode it about 45 mi around 75-80mph and it shut off like the fuel was turned off...bike restarted...makes me think the fuel pump is going south....however...there is always a great vacuum on the tank and the cap is always more difficult than it should be (in my mind to remove)....like it is not venting....this has been going on for a long time....so, when the bike died again, I opened the fuel cap and releived the vacuum and the bike ran fine untill the vacuum had returned....is this normal to have such a vacuum.....I think it makes the fuel pump work harder ...yes //no???

Sounds like the charcoal cannister may be plugged. If the tank is overfilled, the cannister can plug, not allowing the tank to vent. Take that nonsense off and plug the vacuum port on the throttle body and see if that fixes it.

I have an 08 wr250x, but a non-California model.
Original fuel pump and over 11,000 miles on her.

I've NEVER noticed a vacuum on the gas cap when removing it to put gas in.
Turn key, light twist on cap, remove and put gas in.

Sounds like you've got a clog somewhere.
The kind of vacuum you're describing does NOT sound normal for any motorcycle I've ever owned.  

bluzharp wrote:

Sounds like the charcoal cannister may be plugged. If the tank is overfilled, the cannister can plug, not allowing the tank to vent. Take that nonsense off and plug the vacuum port on the throttle body and see if that fixes it.

that could be...I fill the fuel tank to the top

doopsx3 wrote:

[that could be...I fill the fuel tank to the top

I'd bet a cheeseburger the cannister is plugged. The charcoal swells when it fills up with gas and it plugs. You can easily disconnect the line from the tank to the cannister and that will vent the tank. Of course if you still overfill the CA tank, it'll dump fuel all over the place.