I recently installed a ORC racing clutch and like some of you, a groaning sound came out almost everytime i shifted from 4th to 3rd or 3rd to 2nd... or even N into 1st... whenever we re-engage the clutch..

(Note: This is not the whirling sound that comes with most racing clutches)

Ok.. the sound actually comes from the clutch plate coming into contact with the flywheel unevenly... kinda like your bicycle brakes that has been worn unevenly... this is caused by the plate springs being unevenly tightened....

To fix this, you have to remove the clutch/flywheel assembly.... and take out the clutch plate from the flywheel.... on the ORC (Ogura) there are 18 nuts on the inner circumference on the plate itself.. check to see that all the nuts are securely tightened... its is very likely that a few of them will be loose (causing the spring plates to be uneven)... that's why the groaning sound is there... just tighten them all evenly and apply a threadlock epoxy or glue to ensure they dont come loose again... put everything back together n install and try it out... the sound should be gone...