[QUOTE=SirBen;179969]Greetings motorized bicycle gods!
I was thinking of using it to go to a town about 50 miles away on weekends.
I would say go with a 66cc (80cc) engine kit for sure and if you have a multispeed bike then for the best performance for the hills I would think you may consider a shift kit for your bike, I dont have the shift kit yet myself, but I will in the near future because I also live where we have some fairly good hills and my 66cc bike with a 41T sprocket strains a little on a couple of them, the multi gear ratio the shift kit offers will also allow you to run down the flat road at much less RPM's on the engine which will give you a more enjoyable ride because the vibration of these little engines will be reduced and that will be a big plus to you once you realize just how much some of these engines vibrate @ high RPM, you can get a 44+ tooth sprocket to help you with the hills but you will greatly limit you top end speed with the larger sprocket, (So 66cc slant head engine, SBP shift kit on multi speed bike, better exhaust-less restrictive, and with a little luck you will get a very strong engine, mix you up some 32:1 full synthetic fuel/oil mix to start with maybe first couple hundred miles and then go to 40-80:1 and you will have a good set up for the hills and for that trip to town once you get all the little bugs orked out on your bike.
You may get many different opinions on what is the best oil and the best mix, so dont be concerned about all the info. you may get on this topic, just pick one more than likely even though they may seem to oppose each other on this topic they are both right, I run 50:1 Full Synthetic myself but some run Opti-2 oil @ 100:1 with great results, so just pick some and I'm sure you will be just fine, heck you may want to be differnt like some and run what you figure to be 76:1 or something just make sure you use high quality oil and you will be fine in this area.
Hope this will help you deside which way to go with what you ask. good luck with your build and just keep asking questions, there are many great people on the forum that know ay more than I do that can help you on just about any question you may have.