I've been to Sri Lanki myself. My wife & I hired a XL250 and did an independent tour around a large part of this island. Our itinerary was very very similar to the one published on the website below. We visited the same places, had a great time, and even spotted a pair of leopards on the Horton Plains - a rare sight we were informed.
"Our motorbike tours aim to combine the thrills and adventure of riding within the tranquility and beauty of the natural world - and what better place than the tropical island of Sri Lanka.
Riding atop a variety of available Yamaha and Honda bikes, we will explore a set of identified destinations in Polonnaruwa, Sigiriya, Nuwara Eliya, Kandy, and Yala, enjoying the scenery and culture. If you're looking for a unique motorcycle adventure far from home, this tour is for you!"