First off, you need to make sure you are not using an "energy conserving" automotive oil in your motorcycle. These oils are labeled with an SJ type service duty. It contains friction modifiers which reduce drag on moving components. However, in cars, this oil is not used where friction is necesarry I.E. CLUTCH. When using an automotive type energy conserving oil in a motorcycle, the oil is used throughout the entire crankcase and transmission. It will many times cause the clutch to slip because of the added friction modifiers. Use an appropriate wieght motorcycle oil, or an automotive oil that specifically lists a service duty of SG or SH on the bottle.
Second off, Pennzoil is regarded as a low grade oil even for cars. Stay away from it.
First, change your oil and get that Pennzoil out. Second, with a fresh oil in there, see if you can hear if the clicking is coming from a specific point in the motor. Is it top end, bottom end? Left side, or right side? Also, rev the motor up to see if the clicking continues at higher RPMs.