Unless you removed your cam timing chain, there should be no need to adjust the timing on your bike. Have you done any top end work on your engine that requires replacing and re-setting your timing chain?
If you are referring to the spark timing, basically you don't. It is set at 9 degrees. If there is a way to advance it please post it here. I bet a few more degrees advance would do wonders for that engine.
I know the 6V thing makes things complex, but did you guys know the XT200 had significantly more advance built into its CDI unit? Not sure what the lower RPM value was but at 6000rpm it was 35º as apposed to 29º on the TW.