g'day all,I'm havin a few little problems with my xr500.I can't seem to get my bike to idle properly i have changed the o'rings in the inlet manifold which seem to make it run a little smoother.I have also changed the valve clearances checked the cam timing which looks spot on and cleaned the carbs out a few times.When i give it a good rev it crackles and pops on the down stroke then it stalls and spits back out the carby and when i turned it off today it backfired out the exhuast.Besides this it runs and rides fine but won't idle properly or for more than a minute at the most.