JUST BOUGHT THIS HI-BIRD QUAD IT'S AWESOME THE WAY IT COMPARES TO HIGH END NAME BRANDS IT HAS THE EXACT SAME ENGINE AS MY OLD HONDA 200M. THE ONLY THING IS I THING THE VALVES NEED ADJUSTED? WHEN IT GETS HOT IT SOUNDS LIKE IT HAS A SPARK KNOCK BUT ONLY WHEN IT'S BEEN RIDDEN FOR AN HOUR OR TWO. IF ANYONE COULD HELP IT WOULD BE GREAT. THANKS