Well, if I am reading the "expoloded" diagram correctly, I count 23 teeth.
However, www.mopedsonline.com has a 22 tooth rear sprocket:
DYA222586 TOMOS A35 Rear Sprocket 22 tooth for new style Mag & Spoke - $21.95
I am picking up a new Tomos Targa XL on Tuesday evening. I plan on adding the soon to be available. 70cc Athena Speed kit from Mopedwarehouse, (which should include the cylinder, head piston, carb, choke cable), and upgrade it with the Techno exhaust. I also want to do the 27T front sprocket, and then get this 22T rear sprocket from mopedsonline.
I'd hope to break into the 50's with it when all is said and done.