I considered swapping out the original carb due to poor starting, lumpy idle and constant stalling at light and junctions. On advice from Phil Speakman at The MZ Shop I dropped the idea and changed the regulator instead. Transformed the running. After about 6 months the bike started to be difficult to start especially when warm. I rebuilt the original carb with new springs, choke plug, float, jets and most importantly the gasket that disintegrated when I dismantled it. Might be worth rebuilding the existing carb. It starts a lot better and warm starting issue has gone away, plus now gained about 10 mph top end with a rebuilt carb. Plus the throttle now closes faster with a new spring where it was a bit slow to close before. Probably cost less than £20 in parts and about an hour to complete. I would have changed the throttle needle as well if I could have found one for sale. Hope this helps.