I would like to share something interesting with you.
Long time ago back in the early 70s in Czechslovakia there was this prototype of 50ccm motorcycle called Jawa Mistral.
This bike was supposed to get into the production in 1975, but that never happened. It was a quiet interesting bike, it had an engine modern 4 speed transmission and with electronic ignition system and 60W for lights. The engine was able to do 4,5hp at 6000RPM it had a bing 17 carb on it with number 85 main jet and number 35 pilot jet, yet its MPG was 235 miles / gallon.
Long story short the interesting part is that this engine had the same piston , the same rod and the same stroke/bore as the Jawa 207 and 210 mopeds.
Later on when they started to produce the Jawa 210 they have used the connecting rod and the piston from this engine as well as the cylinder insert,
But they degraded the power of it and changed the timing and the sizes of the ports.
Lately i was lucky enough and i have found the factory documentations and the timing angles of the cylinder, I used those angles to set up a port map i would like to share with you. With this map you could get some extra power at good mpg, Nothing drastical for racing, but it could make your moped more enjoyable.
Sadly currently i have no stock Jawa 210, so i cant try it myself, i am building my 80cc Jawa 210, you can follow my project here: http://www.bikepics.com/jawa/21080cc/14/pics.asp
if you have any questions please feel free to ask.