soot in the carbutrator?
 

My 3AJ does the kangaroo move when I push it to high revs (5500+ revs). I thought that maybe there is dirt in the carb so I took it off the bike and had a look. When I looked in the 2ndary carbs outlet (the side thats connected to the engine) there was soot on the walls and on the round flap that pivots when you turn the throttle. I checked with a friend and he said he'd noticed the same thing on his bike. Is this normal?

Thanks