A CB 750 is ancient history ... In the old days it was easy to hop them up ... it is NOT nearly as easy to hop up any modern Jap 4 stroke bike.
If you think it is .,.. you have no clue what you are talking about.
They are already running stratospheric RPMs
They are already running very aggressive cam lift and timings
They are already running very high comp ratios
They are already running huge carbs or injection bodies.
The stock exhaust flow huge quantities with little restriction.
I'm talking the bike motors (not cars).
The modern engines (like this Metro) .. are already very highly tuned .. and most attempts to speed them up .. make them slower.
... and the costs to hop us 4 strokes us way more expensive and more complicated than 2 strokes.... which I already stated.
Go ahead ... knock yourself out .. its not my money.
.. and we'll see if it gets faster ... or slower .. when you are done messing it up.
Make sure you measure the performance first before mods.
(now .. if they have an RPM limiter you can eliminate .. thats another story)