the rattling could be a manner of things so the best thing to do is take off the transmission cover and have a look if you think its from there,there are about 12 8mm hex headed bolts holding it on DONT take the kickstart lever off though it stays in situ.most rattling comes from loose exhaust pipe internals and centre stands rattling on the engine in the stand up position,does it do it on the stand or off the stand or both?
adam bike doctor
January 2010