Topic: Battery dying but battery seems to be good

[luwys]

Hey guys, i am new to this forum and hoping to gain some knowledge on my bike that i am having trouble with. I have a 81’ honda cb750k and it runs beautifully but am having issues battery wise i bought a new battery for the bike as the one it had before was dead and with the new battery the bike cranked over nicely and rode great for a while but a day or two later after a good ride i parked the bike to get some lunch and when i came back the battery was dead. I left nothing on so i was a bit confused i got the battery recharged and everything seemed great battery held charge but when i put it on the bike and had a good ride and parked it the bike died on me again. Im not sure where to start my bike has this weird 2 kill switch side thing so i am not sure if there would be an issue there i hope someone could enlighten me
Thank you!


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[Stev-o]

First off,  welcome.   I believe your bike is a DOHC and this website is devoted to SOH. Models but this check will work on all bikes:

Get your voltmeter and set it to DC.    Start your bike and let it idle, check voltage at battery, should be 12-13V.   Then hold a fast idle at 2500 rpm, check again, voltage should go up if your system is charging, I suspect that it is not. 

Report back and good luck!

[innovativems]

The dohc Honda’s are notorious for rotors and rotor brushes going bad which lead to charging issues. 


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[luwys]

Okay so i put the volt meter before turning on the switch and it was at about 12.47 and then when i turned the switch it went down when i cranked the bike over and running  and began reving to 25000-3000 the voltage read from11.67-12.09 any ideas on what is going on here?


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[innovativems]

Yeah your charging system isn’t working.  Next step, test the ac output of your stator


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[luwys]

What should i look for ?


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[Stev-o]

What should i look for ?

Click:

http://lmgtfy.com/?q=how+to+check+charging+system+1982+cb750

[luwys]

Hey guys so i got the new rotor in there and i tested it and it tested good i turned over the bike and the battery isnt charging up past 12 when i rev it up to 2500-3000 rpm do any of you guys know what to look into ?


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[luwys]

Let mw rephrase its charging up to about 12.3-12.4 on the multimeter when i rev the bike 2500-3000 is this normal or is there something else i need to fix


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[luwys]

Its reading 11.94


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[luwys]

What should i look for?


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[Stev-o]

Here is a very good diagnostic "how to".

Click here....

http://www.oregonmotorcycleparts.com/FAQ.html