Motorcycle Repair: Knocking Honda 1976 CB550K, oil additives, oil additive

Question
I have an annoying knocking sound as the engine warms up it goes away. It is smoking just a little, the smoke is white. The bike runs well and has good power. My question is could I benefit by using an oil additive at the next oil change? Would it harm my engine?

Answer
Jeffrey, oil additives won't hurt anything but I'm guessing it won't fix the problem either.  I'm betting the knocking noise is from a carb sync imbalance causing one cylinder to fire harder than the others.  It could also be the typical clutch knock that some bike have.  Does it go away or significantly reduce if you pull in the clutch?

Regards
Rich