Thanks for being here everyone. While I may be a newb at motorized bicycles, I am by no means a newb at mechanics. I have built everything from lawnmowers to very high performance road racing cars. I have at my disposal extensive tooling. I live in Utah. I am a late 40+ YO married guy. the bike I am building will be primarly use for fishing, camping and cruising around race paddocks. I would like to build something that can haul my fat (225 lb) arse around at say 25 MPH. Remember that at this elevation performance will drop. I have a Trek 990 hard tail mountain bike I plan to use for the pinnings. I had researched and decided that a Grubee 80 with an aftermarket X-chamber was the ticket but I am already questioning things. Please give me bullet points to these questions: >> 2 stroke -v- 4 stroke. 2 stroke is simplistic but will a 4 stroke be more reliable? If so how much more if equally operated and maintained. >> Clutch - I am confused. As I understood things the engine basically was a direct drive with a clutch to disengage the drive. Yea, so how and why a centrifugal clutch? Are they different than say a snowmobile or other centrifugal clutch??? Is it just a nominclature thing? >> Parts and pieces - How much is available and prefered shelf stock compared to custom machining (ie mounts and such)? What spares should be kept on hand? >> Brakes - I need to know the god of friction is on my side!!!!! Can stock bicycle brakes (caliper type) get the job done? thanks!!