There should be a hole through the twist grip , turn the twist grip and you will see a screw holding the end plug. Remove the screw and the plug will pull out.
ES250 Doppelport, ES250, ES250/1, ES250/2,ETS 250, ES150, ETS150, BK350, IWL Pitty, SR56 Wiesel, SR59 Berlin, Troll............ and thats just the German two strokes! http://thecomeconcollection.blogspot.com/