I see there are some know-it-alls on the board. TWO of 'em actually!
Additives are very helpful, and definitely not a waste of money. I don't know what the hell they are thinking by saying they are a waste.
Question: If you fill up your tank and there just happens to be some water in the gas, what happens?
Answer: Once the water gets atomized and sprayed into the engine, your engine will sputter and possibly stall.
Solution: If you know you are getting gasoline from a questionable source, carry a bottle of water remover/octane booster!
Come on, put some logic behind it fellas. Not all products are scams you know... In fact most additives ARE useful products. For instance, the next time you take a trip to mexico or some place and you notice your engine sputtering a little ways down the road because of the low level of octane in the gas, you'll be thankful you had an additive with you.
Also, if you put low octane fuel in your motorcycle you may be causing premature wear on parts. Use an minimum of 87 octane. 83-85 isn't enough, and you may get a heavy knocking. 89+ Octane is what your machine deserves if you care for it, and an additive once in a while to purge the system of any water.