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Motorcycle Repair/Electrical issues


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?  


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...

Mark Shively

Motorcycle Repair

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Mark Shively


Friends, I will be ending my services with AllExperts effective the first week of June, 2007. It's been a pleasure the past few years corresponding with the many of you. Respectfully, Mark Shively (Dayton, Ohio) ""


Graduate of the American Motorcycle Institute (AMI class 172), multi-factory trained technician, 7 years experience dealership technician & service manager, professional roadracing team technician. Court certified expert in area of motorcycle technology. State certified crash investigator. State certified commercial vehicle crash investigator. State certified forensics/evidence technician. State certified instructor; community college instructor. Privately servicing street motorcycles & ATV's, accident reconstructionists, and dealership turn-aways. I am not available as an expert witness.

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