ignition timing advance vs retard ?

a differance in topend or bottom end
my old kawi made a big differance between the 3

Timing adjustment shouldn't be something that needs to vary based on the track!

For any given engine RPM there will be a timing setting that provides the greatest amount of power. As the engine RPM increases, the spark has to come earlier to give the fuel time to burn. At lower RPM it needs to come later so that the piston isn't still coming up when the burn is trying to push it back down.

Ideally there will be an advance mechanism that automatically advances the timing for you as the RPM changes.

Unless your situation is different than everyone elses's, your best bet is to set the timing where the factory suggests it. Examples of a different situation would be running a different fuel, such as alcohol which burns slower, or you have really tricked out the motor to run at much higher RPMs.

Setting the timing late will mainly just reduce power. Setting the timing too early can make the engine hard to start and really hurt the bottom end. While you might see a small improvment at the very high RPMs you would run the risk of melting your piston during a run of WOT at mid range.