2001 gasgas 250 xc makes a new sounds

[acmetrapper62]

I have a 2001 gas gas 250 xc/ ec model it has 300 low hours on it makin a werid ticking or clacking or some type of sound I never hear before idkk if it the top end needs done or my power valves need cleaned or adjusted. U can notice it at low speeds and idle my air filter was real dirty like bad I changed it and I have this problem there was no dirt in the intake I'm running low octane gas and it suposed to run high octane gas idk if my bearings are bad . I change tranny fluid offen I'm using rotella t6 synthetic oil . Idk I have a race in 2 weeks what should do my self before I take it to someone