The number one problem I see on GL1000 carburetors is twisted throttle shafts. The usual cause is overflowing carburetors. Since the GL carbs are without the overflow systems found on most other carbs, it is all too easy for overflowing fuel to back up into the carbs, and into the engine. Along the way, the throttle and choke shafts become submerged. I recently had a job where the leftover resin was 1/4 inch thick, and one of the throttle shafts was actually broken off from the customer's attempt to use the throttle. Stripped out sync adjusters also result from this. Once the throttle shafts are twisted, it is very difficult to sync the carbs.