[THE RED RIDER]

Dear Friends,
During the last days of cycling when the right front suspension in contraction operation(about 50% from the Maximal contraction) There is a sound of whistle without any erasure, also there is no Oil leak from the seals . the motorcycle done about 150 hours and 5100 km.
From Your experience what could be the reason for it?
Is it Could indicate an internal problem in the suspension ?
Thank you all!!