I recently bought a 2000 suzuki quadmaster 500 4x4. the bike runs well but i noticed that it seems to idle high which seems to make it hard to select a gear. also noticed that it tends to backfire when i turn it off but i think its because of the high idle. I looked at the carb but dont see any adjustment screws.. could it be just a dirty carb, or is there a idle adjustment that i just did not see. thanks