There's a gauze type filter inside the tank on the pick up pipe, this could be partially blocked due to the disturbance of sediment by removing the tank. Just take the feed pipe of and loosen the filler cap, blow back with compressed air, just two or three short bursts. Put the feed pipe back on and tighten the fuel cap.......but DON'T start the engine for an hour or so, give the disturbed sediment time to settle out again.
Also check that you've not trapped the feed pipe when you re-fitted the tank.
Hope this helps.
Rob.