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Motorcycle Repair/Electrical - 1971 Honda Sl350-k1


When the key is on and the on/off switch is off, it reads over 12 volts and the neutral light is bright...all is good.  When I put the on/off switch to on...the voltage drops to about 8 volts and the neutral light gets dim.  I have read where this is normal to a certain degree but I think this is extreme.  Also...if I am wanting to start the bike and if it takes multiple kicks to do neutral light gets dimmer quickly and battery seems to drain power.
Assuming my battery is good....and sounds like there is a bad connection or short....what is the best way for me to troubleshoot this?
Wish I could find a motorcycle electric expert in Michigan.

Ken, your battery is bad....

It is holding a "surface charge" of 12v, but when you put an electrical load on it (Ignition switch ON to power the ignition system coils in this case), there is very little current/voltage left to run the bike properly. The cutoff voltage for the coils is down around 9 volts. When you repeatedly kickstart the bike, the permanent magnet rotor is continuing to generate a little bit of voltage to help the battery fire the coils. If you were push-starting the bike, it would have the same result.

You can't assume that a battery is good without testing it. They only last about 2 years in most cases, anyway. So, go buy a new battery, get it fully-charged and you should be fine, unless your charging system is not working properly.

Bill Silver  

Motorcycle Repair

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Bill Silver


Need help with vintage Hondas from the 1960s? I am an expert with 250-305cc bikes in particular and most all of the other pre-91 models, in general. I do NOT claim to have a great deal of experience on Gold Wings, Cruisers, ATC/ATVs and dirt bikes.


I have owned/ridden/maintained Honda motorcycles for 35 years. I have written five books on Honda repairs and collecting. I was a service manager for two Honda shops back in the 1980s.

VJMC (Vintage Japanese Motorcycle Club) of North America

VJMC newsletter, as editor for two years and as contributing editor currently.

3 years auto shop in high school, teacher's aide in Automotive Technology in Jr. College, Diesel mechanic course in college, self-taught mechanic and automotive writer.

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