just to rule out a blocked tank vent. when it starts acting up next, crack open the gas cap a bit, just enough to break the seal and see what happens.

also it may be worth pulling off the petcock and cleaning that out, there is a screen filter in the tank that can get clogged up and restrict fuel flow.

these suggestions assume that it is not a CDI problem (which it could well be). but they are easy to do and will not hurt anything.

05 speedmaster - 1100cc, 11:1 racing pistons, Carillo rods, thunderbike cams, ported and polished head, 2mm over intake and exhaust valves, Barnett kevlar clutch, scepter pipes, oversize manifolds, 45mm HSR's, TTP stage 4 firestarter