Here is a Puch E50 that I rebuilt for a project I am working on.
You can find manuals online.
There is a great tutorial on how to rebuild them here:
After looking at that tutorial and downloading a manual you should be able to rebuild one of these motors very easily.
I got the motor off of a 1978 Puch Free Spirit. I trade an ignition system for the whole bike. The frame was already welded rigid when I got it. First I disassembled the whole motor and cleaned everything up. Then I took the bottom end pieces over to my friend Chris’s house and sandblasted all of the parts. I took great care in not blasting any of the surfaces that the bearings ride in or the cases connected. I bought a new racing crank, bearings, three shoe clutch, Treats 70cc Reed Kit, Malossi Intake, PHGB 21mm Black Racing Carburetor , Treats CDI, 70cc High Comp Head to rebuild it. I ended up putting everything together crankwise. Then a friend needed all the bottom end pieces and didn’t want to wait for shipping. I ended up selling all of the components put together at cost to him.
For the 3 shoe clue I put it in a vice and used weights and a fishing scale to dial in the shoes so that they come out at the same pounds of force. I dremeled out the Treats CDI so that I can have more adjustment. I will dial this in with a timing light later. I painted everything with High Temp Ceramic Paint, so hopefully gas doesn’t take it right off.
All in all it has been a pretty fun project, just kind of slow completing everything on it.
After I put the motor on the intake was going to interfere with the frame. I used a dremel cut off wheel and cut down the intake spigot. Then I bored it out with just a sanding drum. I pushed a copper 90 degree street elbow in its place facing out the side. This worked out really well. I will be able to trim the rubber hose to almost fit the carb on the intake directly. I then sealed it on with some sort of JB Weld liquid goop. I was worried that trying to braze it on would melt the casting on the intake.