Motorcycle Repair: Honda cb400F, field coil, volt meter

Question
It started 2 days ago battery was dead charged it fully, put it back in he start working I rode about 2 hours When I coming to stop sign, every thing turn off. Any way charge the battery same thing happened, if I keep rpm 5000 and up he runs other wise shuts off. what is the problem? Thanks for your time. By the way I changed battery with my friends bike he has same bike it happened again. Please help me.

Answer
I'm assuming the bike runs fine when the battery is charged and dies when the battery gets low.  Put a volt meter across the battery when the bike is running after you have charged it again.  It should read 14.5 volts when reved above 3000 rpm. If it doesn't, it can be one or three things...the voltage regulator, the stator or the field coil.  There' no check for the regulator but you can check resistance on the stator and field coils.  You should be able to find the procedure and resistance specs in a Clymer manual.  

Good luck
Rich