Vacuum in gas tank

[bobgroger]

So the last 2 days have been quite un-Seattle like, and I have been riding. Both days, I parked for an hour or more, then came out, started the bike, and after a couple blocks it died. Yesterday I futzed with the petcock, moved it to PRI, and eventually got it going again. Today I had the bright idea to look in the gas tank. Opened the cap and there was air rushing in when I removed the cap. It started and ran fine after. I know there is a vent hose on the tank in the fuel sender, is that likely plugged? Or maybe I need a leakier gas cap....
The tank did sit for 18 years with the same gas in it, but it cleaned up pretty well and there was minimal rust. Petcock is new OEM. It runs perfectly other than that, all of the newbie issues have been covered extensively.

[tkent02]

Yes the vent is likely plugged, no it's not in the fuel sender. That one is a drain, in case the sender leaks it goes harmlessly overboard.

The vent is in the keyhole.

[chuck hahn]

Take the black plastic cap off on the inside. Then youll see a brownish kidney bean thing with a big ball bearing held on by 2 screws take that off..be carefull because theres another smaller BB under there too. the remove the browm disc thing with the hole in it.

Now youll see a hole in the body of the cap...spray carb cleaner and lots of air in there to clear the vent passage thats milled into the cap body.

[bobgroger]

Thanks, guys. I NEVER would have thought to look there.....Out to the garage right now.

[bobgroger]

You were spot on. At the bottom of that almost Italian pile of complexity is a small hole plugged with 34 years of gunk. Gave everything a good cleaning, and lubed the lock mechanism although the gas will probably wans the lube out by tomorrow. I'll bet that is responsible for a huge number of lean running complaints.