Hello everyone. Got a question Im hoping some of you may have previously encountered or may be able to shed some light on for me. I have an 89 k100rs with 63k on her. When i start it up cold it makes a bunch of knocking and grumbling noises until reved up above 1500 rpm or until warm up is complete. After reading numerous posts and many forums looking for an answer to this problem I decided to disassemble the bike to correct any issues that may be causing this noise. I have it apart to the block with the cam crank and chain covers off and everything on the back end including fly wheel clutch etc. In this process I am not finding anything that would be imediatley evident as the cause. I did not pull the block and look at the output shaft but I can see the gear mesh with the crank gear and there is no slack. I can see the rivets and there is no visible slack in the rivets. At a bit of a loss at this point as to what the noise might be and I hate to reassemble the bike and leave the noise after going this far. Any ideas or advise would be greatly appreciated.