After being here a while, as many have been, we see a lot of the same questions that seem to come from a place of general misdirection or lack of understanding about where to start when upgrading a bike. Perhaps this may act as a general place to start, because I'm bored and maybe some of you noobs need direction. Where to begin?
many people come on here with no real direction and ask questions like "is this pipe better than this pipe?" or does a "high comp head make me faster?"
Basically, you're just approaching the entire thing from the wrong direction. You need to get a better understanding of what makes bikes go and what you are trying to achieve, then you can decide how your bike should be modified or if you should use different parts.
Step one: read. Get a general understanding of how a bike works, then most of your questions will seem obvious.
Step two: what do you want? Most of you want more speed or accelleration. so what makes speed? It's basically a function of power and gearing. Increasing power makes for a faster bike, and then you can use gearing to alter how that power is used.
At the most basic level, you want to determine what your speed goals are, and how you plan to get there. For the sake of this tutorial, let's assume we have an e50 that we want to hit 50. There are two basic approaches, a high rpm bike with short gearing or a lower rpm bike with taller gearing or somewhere in between. A high rpm bike will likeley be the faster of the two If mostly equal because Rpms generally produce a higher overall level of power, but a lower rpm bike may be more pleasant to ride fast. For this example, I will choose a lower-mid rpm build as opposed to a screamer.
Step three: make a plan. Because I want a lower rpm bike amd this is a one speed, I will likely want to use a 70cc kit. the 70 kit will give me better all around power to work with which is important for my one speed. I could go 80, but for the work involved an my modest goal of 50, it is unnecessary. So fuck it, I choose a mk65 because they arent fancy and have a basic port design and flow well for low Rpms. I determine I'll probably need 18x45 gearing to hit 50 by 10k Rpms, and I'll use a good all around pipe to pull that gearing from relatively low like a proma or estoril. At 10k I'll probably be ok with a stock crank, and a 19 del will probably be satisfactory, but anything under a 24 mikuni is probably a fine choice. A 70cc head is something I like to use because it
has a much better design than stock but you might get away without it if you are a cheapskate. Notice I didn't say anything about a cdi. Fuck a cdi.
Step 4: setup. For this simple build I wouldn't do anything to drastic, probably split the Case to port match, measure some gaps (see proper engine assembly) and throw it together and TUNE( see tuning). From experience this setup should hit close to 50 if properly set up. From here, I would port the exhaust to taste if I want more speed. Viola! A kinda fast bike!
I am aware that there is more to the more advanced builds. This is merely an exercise to explain that it isn't so much as one piece is better or worth it or etc, but that you have certain parts at your disposal that you may choose to utilize or not to. The question is, what are you trying to achieve, and do you understand how tuning, modifying, or using different parts helps you reach your goal? Because this is where to start.
Feel free to add
Or critique as long as you realize this isn't supposed to be an all inclusive guide. Hope that helps someone get started.