some sort of frequency noise ?

[moley]

Hi guys . I have just got back from a weekend away and I have a question to ask . My CR is approaching 19000 miles and  starts and stops as it should but a strange sound has developed between 30 and 40 MPH .Its sort of like a frequency rumble so Im assuming its coming from a moving part i.e cam chain , clutch basket etc . It doesnt affect the bikes performance but I can actually feel it through the foot pegs ! Once I am past 40 mph it goes away .Was wondering if anyone else has experienced this and might know what the noise is coming from . It  only happens once the engine is up to full temperature so its when the oil has thinned out . Pulling the clutch in does not change anything which sort of rules that out but after a long ride I can here slight play in the clutch mechanism once I  get home and its ticking over on the  drive and pulling the clutch in then does silence the play ....Im a bit confused to say the least

[moley]

Hi again guys . I have just seen a previous thread for almost exactly the same thing aand its been related to the chain tension so I will start with that first and see what happens ....cheers