Yep, the bigger carb, even with the offset intake manifold, will hit the tank. There are a couple of alternatives for you:
1. Move the tank back 1" and raise it 1", and then replace the petcock with one with a 90 degree outlet to the back. TrailBikes has one on their website HERE.
2. Pick up a 12-way adapter that allows you to rotate the carb and manifold out 90 degrees to the engine, like THIS ONE.
I have a '77 Z50A that I use as an R&D test bike for engine builds, to break them in and run them. It has both 6V and 12V electricals on it, so I can test either points-type engines or CDI-type engines. The tank is raised up and back 1", as shown HERE, to give you an idea. I also made "L" brackets for the seat, to move it back 1".
ok thanks man. what are some front end options for my bike i know in the rear im installing an xr75 swing arm but i dont know what to do for a set of forks? what is the front end set up you have on the z50 in the picture and what wheels are you running on it?
With the right wheel spacers, the CT70 front wheel will bolt right up to the Z50 forks. The same goes for the rear wheel when using the XR75 (or 80) swingarm. The XR/CRF 50 wheels are 10" front and rear, but the rims are only 1.40" wide. The CT70 wheel will not fit on the XR forks, either. HERE is a pic of my '83 Z50R with the XR80 swingarm and CT70 wheels. That isn't a stock 50cc engine, either.