Just picked up a 1995 cbr 900rr about 2 weeks back. Im having this sound (sounds like a marble hitting a wall), coming from my carborators. Im wondering what I could do to stop the noise. A friend tells me its something lose like the valve. Another friend is telling me the timing might be off. All I know is when its idleing you can still here it. When I ride, it rattles more. It feels fine but the sound is so iiritating. Can anyone figure out what this noise is?? Also forgot to mention my bike has aftermarket carborators, and no airbox.

 

What are the intervals of the sound? meaning, how often does it make the noise... every 1 sec.. every 5 sec...

how many miles on the bike?

there shouldnt be anything in your carbs that will make the noise you are describing. I would lean towards the valves... possible timing chain tensioner.

Im not sure of the ill effects on your airboxless motor. usually, you will loose performance without an airbox.