weird knocking noise

I'd like to know your opinions on this.

So I did my oil change, carburetor clean up and changed my brake fluid (dot4) on my clutch handle on my vfr750 1991. But there is a knocking sound that comes from the engine (I think it's the clutch that has a problem). I can only hear the knocking when the engine is on idle up to 2000 rpm, after that, everything sounds good. The knocking sound disappears when I press the clutch.

I was searching on the website to find if someone had something similar and i found this. I don't know if this could help me.
http://vfrworld.com/forums/showthread.php/22135-Starter-Clutch-Repair-VFR750-With-Pictures

What do you this is the problem? and should i follow the guide i found?

 

you should check it out, may also be the clutch basket is worn

 

I concur with worn clutch basket. Starter clutch only makes noise upon cranking, being part of the starting system. How many miles on your bike? My bike has 43k, and I noticed a little chatter behind the cover.

 

Sync your carbs first. Out of sync carbs=oscillations@crank=noise @ clutch basket

 

As Grey states, noisy running at idle due to poor carb synch or uneven cylinder compressions causes the tabs on friction plates to brattle within the clutch basket as the engine constantly changes speed at idle.

Carb synch needs checking/adjustment.

 

good catch guys....did not think of that

 

I'm not totally sure about a bad carb sync because the knocking sound only comes when the clutch is released.