WD40 would be an OK way to clean the chain and sprocket, but you should use real chain lube. While Triumph use a sealed chain, there is still friction between the ends of the side plates, and that needs proper lubrication.
If you do a serch for chail oiler in these forums, you will find a few threads about automatic chain oilers. There is an automatic one available called the Scott Oiler, and a much less expensive one that is similar in operation except that you have to reach down and give the oil bottle a squeeze once in a while.
