I had a Mustang that would do that. changed fuel filters, checked carb., changed the coil... It ended up being the part # tag on the fuel gauge sending unit got loose and would wrap its self around the fuel pick-up inside the tank, after awhile it would fall away only to be sucked up again. Granted the fuel pump was sucking this tag around the pick-up and on the bike it's gravity fed, but I would look INSIDE the tank too. Next time this happens, shut the petcock off and check for fuel in the bowls just to eliminate if any thing is wrapping it's self around your fuel outlet, like a piece of plastic wrap.
