I used that item on my xs650(It's a rectifier available from radio shack for 3 or 4 bucks if I recall) - having the connector and wires already on it is well worth the $22 unless you just LOVE to diy stuff. If your bike has the old selenium rectifier, the silicon rectifier will improve the alternator output. If you have the silicon rectifier and it's still OK, you will see no improvement.
These are the units before I wired them in and put connectors on them(XS650 needs 2 of these instead of 1, 1 more pole on the alternator)
They are at the top of the picture. You would just need one for the old CB.
Pamcopete has researched and solved a lot of the electrical gremlins on the xs650 and also makes a spiffy electronic ignition for those bikes.
http://xs650temp.proboards.com/index.cg ... hread=3473
The wiring does NOT apply to the honda twins , so don't follow that thread-but as you can see the low dollar approach does work.
