If you are interested in renting a custom in Chiang Mai you do not have many choices. Just came back from a quick trip to Pai and one of my friends rented a bike at Moon Muang at a small shop where they have just 3 bikes, a Suzuki GS 400, a Honda Super4 and a Steed 400. He rented the Steed and it was terrible. Owner did not want to take responsibility and we ended up paying the full rental amount although he had to stop 10 times on the way to Pai because engine overheat and so our trip was spoiled. Last month another friend rented ad Big (or Bad) Shopper and also a bad Steed. The only shop I can recommend is Jaguar on Moon Muang where they have a Steed 600 and a Steed 400 both in good condition.
Hans
Hans