I'm back on the road!... Sort of..Vacuum problem?

Hi all,

As you may know from earlier notes. I have been rebuilding a 99 Interstate that I went for a low speed tumble on.

I had the bike inspected last week and it is now on the road. Today I rode to work 32km (20miles).
The bike was good, I'm a little rusty at the wheel. It has been 18 months since I tok that tumble. This new version has a 6 degree rake kit and I have gone to the dark side. So this was my first ride after the inspection with the car tire.

When I went to leave and go home, I started the bike with full choke, it started and run rough for about 30 seconds then died. It would not restart.

After several minutes of trying to start it agin and figure out what was up, I opened the tank cap while listening for a vacuum sound. I heard not vacuum as I opened the cap. But the bike started with a few more cranks and I started down the road.

The bike was running very poorly. I had to keep it revved and it sounded terrible. I have never heard the bike sound so unbalanced. After a few blocks I stalled again. I opened the gas cap and restarted the bike. I rode 20km to a autoparts store and bought a strong carb cleaner additive and added it to the tank. I locked the cap in place and went for a ride and then home.

When I got home the bike was running perfectly, gas cap in place.

Anyway, I'm stumped. Seems like it might have been a temporary air lock.
This has never happened before.
I'm looking for ideas.
Has anyone ever had this sort problem?

Best regards,

Glenn

ps. I know I owe some pictures of this project. They are coming. I purchased a new digital camera that will not communicate with my computer. She is looking good.