I have a Gilera DNA 125 and half of the spark plug has snaped off, inside the bike. basically all of the thread is still left in there. i have the rest of it out, but i dont know how to remove the thread without having to drop the engine out and removing the head. has anyone got any suggestions. if so then i would be extreamly grateful. ive tried pliers, and a screwdriver. but its in such an awkward place i dunno wot 2 do, i would drill it out, but i cant get a drill in the small gap.