hi...
it has happened to me b4 too...
there is nothing wrong with it but usually this happens when u rev it in neutral...
never encountered it when rev till redline in gears....
HKS SSQV Universal for sale.
Bought brand new RM700 (including adaptor) from M-Power at Air Itam, Penang.
Used for 3 months only, 3,500 km travelled, very good condition.