Dan you might try removing the gas cap when it is acting up. Karl, (Crossbolt) had a similar issue with his DT and when he removed the fuel cap he heard a wooosh. He found that the venting valve, for the fuel tank was stuck. His post about it is on here someplace. His remedy was to disassemble the cap and put a small hole in it. If you don't hear the wooosh, then that's probably not your problem.
I love the combination of color on your BW. It is styled some what like the Wing. I've owned two Silverwings and they are great bikes. About 500 lbs. as I recall. Good luck....
Mac, aka "ole two wheels"