Here is my understanding how the secondary transmission ratio and acceleration works.
Based on my strictly scientific research because of looming chain and sprockets change
If I increase my secondary transmission ratio say from stock 15/48 I go for 13/53 sprockets, the bike will have more acceleration (foots per second) and pulling force (lb per foot).
Obviously you can't change the torque or the engine power. Engine delivers different power during different RPMs. The engine power/torque to RPM graph is constant. The graph below shows 2 lines one is for torque (nm) and the other is for power (hp) during different engine RPMs. BUT the graph is the same for ANY ratio!!! That means engine produces some amount of power when doing some RPM and you cannot change that. You can change only how you transfer that finite amount of power to the wheel using the gears (and the final drive ratio):
You ONLY can change the way how you transmit the power/torque to the wheel. The variables are only acceleration (foots per second) and pulling force (lb per foot).
Say with the stock 15/48 in second gear doing the same RPM say 4600 I will have 10 fts2(foot per second squared) acceleration going with 31 mph and the pulling force will be 210 lbf.
With the custom 13/53 in second gear doing the same RPM say 4600 I will have 14 fts2(foot per second squared) acceleration going with 25 mph and the pulling force will be 270 lbf.
Here is the way you change the power delivery for the above example for second gear:
[url=http://motorcycleperformanceanalyzer.com/yamaha/fzs-600-fazer-1998/]http://motorcycleperformanceanalyzer.com/yamaha/fzs-600-fazer-1998/[/URL]
You see clearly what you loose transforming your constant power into higher acceleration and more pulling forces - you loose the top end speed. The peak for high ratio 13/53 is around 48mph compared to 64mph for standard fazer 15/48.
If you look at moto gymkhana you will see they use ginormous sizes for rear sprockets - they need big acceleration and not much speed obviously no motorway commuting during the gymkhana LOL. Simples.
[/url]