I have a ninja 250r with about 20000ks on it. When I'm going down through gears 3 and 2 coming to stop I can hear a chk or a tk sort of sound every half a second or so for a couple of moments. It's pretty quiet and I can only just hear it over the engine noise. I was thinking it's just some light rubbin of the machine somewhere.. I can't see where but does that sound like something I should get mechanic to have a look at now or just wait till the next service in 4000ks? Thanks for any advice!