By far the best mechanic in Hue, if not the best in Vietnam, is Mr Thien. Not only is he as honest as you can get, he is pretty handy with fixing all types of motorbikes from highend scooters to every Vietnamese backpackers favourite Minsk or Honda Win.

He is located close to the backpacker area on 24 Nguyen Sinh Cung, Hue City or view him on Baonhieu.net here: http://www.baonhieu.net/useful-information/kim-thien-machanic/