I recently did some upgrades to my 2001 warrior.I put on a new pipe,high comp piston,heavy duty valve springs,cam,air filter and modified the airbox.when i reve the engine and when it is under a load there is a loud cracking sound comming from the engine area and the air box area.I did a plug check and I think the jetting is correct(maby a little lean).Is this a jetting problem or something else? thanks for your help.