The CDI from a 1996-1997 XR400R can be fitted to the XR650R. The XR400R CDI is known to produce a noticeable difference in higher revs on the XR650R. It is said to run cleaner and peak slightly higher. It does this by advancing the timing a few degrees and extending the rev limiter. (Part number 2650, NOT part number 2740).
The CDI is made by Denso and the Denso part number is 070000-2650.
The CDI can also be purchased through Honda with the Honda Part number 30410-KCY-671 or 30410-KCY-761.
The female pigtail connector on a Honda XR650R CDI looks like this:
ONLY the 1996-1997 XR400 CDI will work. Other models are incorrect.