Oil Additives

Bikes are not like cars in that they use the same oil for both engine and gearbox. If you use an additive it could (and probably will) glaze up your clutch plates. Most of these additives are friction modifiers. Definately not what you want to give your clutch a bath in.

Use a top quality oil specifically for motor cycles and stick religously to oil change intervals and you cant go wrong.

don't add anything but oil, decent quality motorcycle specific (for the wet clutch) oil will do the job. oil has a detergent/dispersant package designed to trap and coat foreign particles and molecules, like carbon and other bi products from the combustion process, if that package is used up on your additives there's nothing to protect your engine from building up deposits and causing excess wear.

paul.

Don't do it! If it is only 3 weeks old it is still running in and it will never do that properly with that stuff in it.
Fully synthetic oil doesn't need additives and some can actually ruin the oil.

As far as I know no SD has ever seized or gone bang due to oil as long as it has the proper stuff in it. I would worry more about setting my suspension up or riding it in salt spray or so.

Use good bike type synthetic oil as per manual and you shouldn't have any problems.