Hello!

When I accelerate with my -94 cbr 900 I feel kind of clacking/knocking on left foot at 2000-2500rpm. It goes a way with more rpms. And it's almost only at 1st and 2nd gears.

I lifted my bike up to hear it but it knocks only when driving real, not lifted...

What could it be?

 

Chain binding/slapping?

Chain slack set right or maybe worn and/ or worn sprockets?

 

I get it also, in 1st and 2nd mostly. I am thinking it's my chain as zaqwert said. My old chain was pretty slack and was making noise. Replaced it and it went away. The current chain is binding at the master link and I am hearing it again. I live up a dirt and gravel driveway, and it's about 500 feet long, so my chain gets very dirty. Also, I have neglected it lately also. I know, bad owner. Think it's time for a new chain, although, going to give it a major cleaning today or tomorrow.

 

Just cleaned my chain and the noise went away. Try that and see if it helps.