I changed my clutch lever out for a new one a few months back. Ever since, I've been hearing a fluttering, "clacking" noise coming from somewhere underneath my tank, when I pull in the clutch all the way with the bike in gear. I took off the small micro switch near the clutch lever, and cleaned the two wiring connecters that plug into that switch. No improvement. I took the switch off again, and tried to clean the very small contacts located inside the micro switch. Still no improvement in the clattering noise. Since I figured it was the flapper valve that was intermittently opening and closing at a medium-high frequency, I lifted up the tank and pulled off the vacuum hose to the flapper solenoid. Problem solved. I plugged the vacuum hose up good, and my test ride revealed that the problem has gone away. I think that rather than trying to replace that micro switch, I will just leave the flapper disconnected... 🙂