Originally Posted by All yamaha
the back sprocket is from the old frame and i guess front is with the yzf.
I would say this is the main cause of your problem. The front and rear sprockets being from different bikes means that each sprocket has a different wear pattern. So everytime the chain goes around the front sprocket it tries to take the shape of the front sprocket. Then when it gets to the back sprocket it tries to take the shape of the rear sprocket. So the rollers on the chain are being bent and ground down between the two sprockets. As a result the rollers will no longer be able to move freely and this will cause the chain to bind when it tries to go around the sprockets. This can make the knocking noise that you are hearing.
Once you get your new chain and sprockets on the bike clean and lube them every 300-600 miles and keep the chain slack around 35mm and it should last you for thousands of miles.