just bought a 00' yz250-starts of the first kick, but has a sound comming out of the left side casing..like a metal on plastic sound, i have not torn it down to see, but does any one have anyidea what it may be, sounds like metal on plastic..my bro said it was just hte sound of the piston, but that does not sound very convincing..just a light knocking noise..like metal on plastic, and when u rev it up it goes quciker?