Thanks Gabe, Gas tank is not rusty, I'd had the petcock off and flushed the tank with some old gas. there was rust built up in the petcock screen but I cleaned that out. Flow to the carb from the tank is OK.
I did try engaging the choke while it was running and that acually caused it to bog 'worse', no accleration at all.
There is no air filter on this bike. I was running it on the stand and covered the intake with my thumb to restrict the air comming in but that also made it run worse.