Just for your historical elucidation: When the Duopar abruptly vanished off the market, someone had to step up to the plate. Especially considering that mountain-bikes were the rage. Everyone wanted a triple up front, and as many gears in the rear as was possible. The 18 spd. was born. And the Duopar would have been the logical choice for it's range, but it really was to delicate for screaming down mountains. Enter SunTour -

The SunTour Mountech came out around 1983, as I recall, and it had the range to accommodate the new MB rage. So we all bought one (or two). These beasties had enough range to likely handle Campy's new 11 spd. with a triple front. And SunTour was happy as they were at war with Shimano. But after raging success - it was found that the spring in the weird upper-pulley that the Mountech had would spontaneously self-destruct. Sometimes violently enough to cause crashes.

With that , and other things that went wrong, Shimano ended up winning the war. And SunTour rode off into the sunset. I still have a Mountech in excellent condition - living in a baggies. Pity - they were excellent derailleurs.

By the by, I could back-pedal and roll my bike backwards with the Duopar. Check the adjustment angle.