Hi I did the same thing with mine got loads of advise from loads (thanks guys) put new plugs in & started first time after I fixed my cock up I put the vac hose on the wrong spigit on the tank so the fuel was not going through. So if you have had the tank off the bike make sure you have put the vac hose on the right spigit on the tank. Hope this helps.
Rob.

Yeah, vac hose is in the rigt place. before yesteray it has all been running fine.

hopefully it is just the old plugs being tempermental and the new set will resolve it.

just to finish this off, new plugs sorted it.