Originally Posted by vonericson
Awesome and thanks for all the great feedback! I think I'll give the 80 a shot, swapping out the OEM carbs right away same with plugs, air filters and finally rounding off with a nice little tune pipe and gearing down with a smaller sprocket for a bottom end boost then I guess I'll just have to keep my fingers crossed and hope they will stay upright pulling hills! If nothing else it should be a fun learning (slightly expensive) experience for myself and my brother in law.
Quick side note, I got my hands on a wrecked Yamaha 750 (totaled front end) for dirt cheap and I've got my eyes out for a used trike bike that I have some insane plans in the near future for and possibly a laydown recumbent racer concept I'm working up in AutoCAD I'll keep posted as I update these!
I would recommend keeping the NT carb and tuning it by a jet size reduction, plug wire and boot is good to chnage up front and a sbp expansion exhaust is a good choice.
You mentioned a smaller sprocket to " boost the bottom end" a smaller sprocket actually reduces lower end pull and increases top cruise speed, get the engine broke in and learn more about it by tuning NT carb which is a perfect little low maintenance carb for these engines, I have a bike with the 66cc/80 china girl that cruises at 42mph and it still has the NT carb.
Do what you want to do to it by all means, but most of us who have been tinkering with these for a while will likey recommend it a good idea to just keep the NT carb at first and get the engine set up to be as reliable as possible before a carb upgrade.
Best wishes with the build.