There is a local A/B rider around here that I see on a brand new KTM 144 (the factory 144's). I've only seen him at practices, but he really rips it up on that thing.
So far in my short (23 ) year life I have worked on enough mechanical / electrical things to learn the following things.
a. Never work on your car/engine/etc while in a hurry. (Loosing a tire going down the freeway in a 1967 SS camaro will teach you this pretty quickly)
b. The respected people in your given industry / hobby are respected for a reason. LISTEN TO WHAT THEY HAVE TO SAY.
c. Take what everyone has to say with a grain of salt (even the experts in b. ) :)
d. Take time to understand the theories behind how our toys work, it will help. (I saved my dad a large chunk of money this past weekend, when our 2t fuel injected boat motor acted up. I understand 2t operation theory and was able to point the problem out. A problem that would never have occurred on a 4t)
e. Last but not least, don't half arse it! Do it correctly and professionally or you will end up doing twice.