Do you have the feeling that your motorcycle is holding back on power, the source may be easier than you think.
Is your throttle cable adjusted properly? If the throttle valves aren't completely open when the twist-grip is fully turned you'll never get max power out of your engine.
Get access to the engine end of your throttle cables where they operate the pulley that turns the butterfly valves inside the throttle bodies or, on older motorcycles, the carburettors. Make sure that when you turn the twist-grip fully back the pulley is turned completely so that the butterfly valves inside are perfectly parallel to the airflow inside.
There are normally cable adjusters near the twist-grip and the pulley, and if you need to take up and slack or free play simply make minor adjustments at both ends of the cable.
Another problem can be your brakes, brakes are there to stop you. But if they're neglected, they can bind and drag which will soak up your precious engine power. Put the motorcycle on a rear-stand or get a friend (maybe more then one depending on the size of your motorcycle) to lift it up onto the side-stand, and try spinning both wheels. The rear wheel will obviously have some drag from chain , but the front should spin pretty freely. If you feel any drag, then give the brakes a fettle. The steps will vary between motorcycles, but essentially you need to remove the brake pads, push the pistons back in, and clean away all the dust and grime in there. Pump the pistons out a little to make sure they're clean, and push them back in before putting the brake pads back in.
You've seen how filthy the front wheel gets from brake dust, so you can imagine what the scale of griminess is inside the caliper. Get in there and clean, for all your life could depend on it...