http://www.thumpertalk.com/ Thumper Talk is a great forum that you can ask pretty much anything about a 4 stroke dirt bike … I would advise you to search thru their forums first as it’s very possible the questions you have are already answered…
or if you have a KTM … http://www.ktmtalk.com/ which focuses mainly on KTMs
40 plus years racing, riding & wrenching bikes