Re: hey guys
Howdy Tony, welcome.
Is a huge question. Best I can tell you is look at the many great builds and how-to's in the DIY section. Also look at the kit threads. If I may be so bold, fast and bicycles are not a great idea. Folks can get amazingly fast speeds but are usually well experienced builders and bicyclists.
Also, be sure to check your local DMV as to what size engine and speeds allowed. A larger engine may not get you any higher top speed (depending, is a broad statement) May just give you more power. For instance, many 50cc engines could run circles around my 79cc and vise-versa.
That was not a lot of help, eh? Best I can do is suggest read, read and read some more.
Again, welcome and ride safe.