I am new to the dirt bike world but not to the 2 wheels . Been riding bmx and downhill for about 15 years ( like you want my back story ) I recently purchased an 07 yz450 last Friday . So pumped I have ridden it every day . It runs great that I can tell but when starting it and idling and riding I am getting a humming noise from the engine area. Is this common on this type of dirt bike. Just wanted to see if I should have it checked out. The guy I bought it from babied it and serviced it regular . By the looks of it he never rode it as there were no scratches. There are now lol . I want to make sure I can keep on going out in the Palmdale hills every day like kurt did. Sucks it took me so long to get one . I have been missing out .