Motorcycle Repair: Electrical issues, regulator rectifier, yamaha xs850

Question
I just picked up a 1980 Yamaha xs850.  It seems that the battery
is not charging, nor does any of the lights or horn work.  I'm not
100%, but I'm thinking the problems are related.  Other then
these problems the bike run nice, until the battery goes dead
from not charging.  Any ideas?  

Ryan

Answer
Hi Ryan,

Test the charging system by performing an output test. Connect a VOM to the battery terminals and read charging voltage at idle, and at about 3.5K rpm. In general, voltage is about 13.5 VDC at idle and increases to between 14 and 17 VDC above 3.5k rpm.

Get the service manual and follow testing procedures. The manual has specific output voltage specs for your MC.

If test fails, test isolate and individual check each component of charging system until you locate the defective part(s). Check altenator, regulator/rectifier, battery, conductors, switches, etc...

Respectfully,
Mark Shively