I determined that the cap was the issue..... This part is about my discovery, so you don't have to do this..... I drilled a small hole in the centre of the cap.....I was able to get air to pass from the centre hole to the breathing hole.....
I have what seems to be a related issue with my F2, so I'm hoping that someone out there will help me revive this thread.
When my F2 first came to me, an oil change revealed that the existing oil ran thin, and it reeked of gasoline. Also, the bike wouldn't start easily. I'd get a *click*, or occasionally the engine would turn over, but nothing else. The former owner suggested that when this happens, I should put the tranny into top gear, roll the bike backwards a few feet, and then try starting again. This helped - somewhat.
I've since determined that doing two other things after running the bike help even more: 1) Turning the petcock to "off" and 2) Opening the keyhole door on the fuel cap (I can hear a "hissing" noise when I do this.)
Remembering these three tricks helps most of the time. They certainly help avoid the gigantic puddle of fuel that used to form under my bike after every engine run.
However, the bike still stalls intermittently while riding. I'm too much of a newbie to ascertain if my shifting has something to do with the problem - I'd not be surprised if it did.
Still, I also suspect that when the bike stalls, the engine is flooded. After I try starting the bike a few times with the throttle held open, it starts up VERY sluggishly. After a few seconds, it smooths out, and I get underway.
Is my tank pressurizing itself when things get warm? Is this forcing fuel past the petcock into places it shouldn't go when the bike isn't running? Bartman352004: In one of your posts, you say: "This part is about my discovery, so you don't have to do this....." Does this mean that you do NOT recommend drilling the hole on the underside of the fuel cap?
Any help that you guys could offer would be MUCH appreciated. This F2 is my FIRST BIKE EVER, and I love it! I've been able to fix other issues on it (carbs have been taken apart and cleaned, rear brake lockup eliminated) pretty easily, but this one has me STUMPED.