Here are some things to test and check on the charging system. When the engine is running, set your voltmeter for 20 VDC and put the leads on the correct terminal posts.(Red positive+, Black negitive-) With the engine running, you should be reading anywhere from 14.5 to 14.8 VDC. (typically this test is done at 5,000 rpms) This tells you your charging circuit is good. If the voltage is higher, the regulator is bad. If you’re not showing a charge and you've replaced the rectifier, you may want to do a test on the Magneto/stator/charging coil. If you’re not a premium member and you don't have access to a manual, this test will be hard to do without it.
There are 2 fuses that protect the charging system. Check the 15 amp fuse in the MPEM and the 15 amp fuse between the solenoid and the MPEM.
I hope this helps you out ...keep us posted.
Karl