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1971 CB350 - Wife's Build, 1978 CX500 - My build
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Discussion Starter · #1 ·
Finally got The Wife's Bike® on the road on Wednesday. Started almost instantly with the electric start. Thought "I should do a little shakedown ride" so I took it the 2km's to the mall to meet her after work.
She comes out from work, and me goofy with pride says "and look, it starts almost instantly"...press the button... a slow whir and then nothing. Headlight is dim, signals won't flash. Luckily it starts on first kick, so that makes her happy. Riding suddenly it's surging a bit. Then evens out and rides really neat and fun. (this is the first time it has been on the road in decades apparently). I get to the gas station to check tire pressures and now the voltage is worse. No headlight at all, won't kick over. Luckily a very brief bump start and off I go and nurse it home.

This is a 1971 CB350
Brand new battery.
I don't think it's a charging issue, because it happened so fast, but I could be wrong, it happens (often)

Thoughts? This bike is supposed to get certified on Monday, so I'm really grasping at the moment.
 

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You may want to do the charging trick where you combine the white and yellow wires coming off of the stator. That way the stator puts out max current all the time, not just when headlight is on. That might help.

Other than that, you can look on this website to figure out how to check the status of your charging system, including how to check the stator for correct voltages and whatnot.
 

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Blimmey, so you got the bike, did the old owner start it for you ???

You rode it to gas station to check tyre pressures !!!

Living dangerously ....

So, with "normal wiring ", a fully charged battery in good condition ( a new one not the ten year old one ), start engine and allow to run a few minuets.

Using a multimeter set to say 20volts DC, connect to battery.

With engine running at say 3k revs, what does the meter tell you ?

Over 13.2 volts ?

At 6k revs, what does it tell you, a little more but no more than 14.7 volts ?

Repeat test with lights on full beam, similar but a fraction lower readings ?

Voltages suggested are ball park, check what manual says. The manual will also have a wiring diagram....
 

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74 CL360, 81 CM200T, 85, 86 & 87 CMX250. Invisible to cages, treat accordingly. Avoids Road Rage!
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I had a problem similar to this on a Rebel 250. The hot lead from the battery was rubbing on a piece of metal and shorting out the battery. This was happening before the fuse box. After rectifying this issue it no longer occurs. Out of curiosity was the battery hot or quite warm when this happened? If so, I would look for a short between the battery and the fuse box.
 
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