I'm here to tell you about the Sachs 505, one of the widespreaded moped engines in Germany.
First, there many many versions of it.
These engines are avaible with kickstart (footshift only) and pedal start. In Germany are 2 Versions, Mofa 25km/h, with the letter B, and Moped 40/45/50 km/h with the letters C(40km/h) and D (50/45km/h). A was used if i'm right only at the 504.
The avaible kits are:
65ccm/43mm Autisa (very old)
70ccm/45(,5??)mm Malossi (out of production)
80ccm/48mm Zeta (out of production)
80ccm/48mm Gringo by Mopshop, produced by Eurocylindro (out of production)
80ccm/48mm Athena/Eurocylindro Membran
To reinforce the clutch, you need a third disc or a second spring.
This is the exploded view of an ordinary clutch:
And this is an exploded view of an 3 disc clutch, which was in some 505:
You see, it has 4 steel discs and 3 clutch discs.
But if you build in the discs, your pin's (no 14) would be too short. They must be 19,6mm long, and 3mm in the diameter...
If you reinforce your clutch this way, it tuning will be no problem ;)
I hope that I could help you... and if you have questions, ask me :D