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Offline mazingerzeca

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battery not charging
« on: October 03, 2014, 05:28:22 AM »
Hello all.
My CB750 K7 is having charging issues. At 5000 rpm it barely reaches 13v (measured at the battery with the lights off). The battery is OK, I've been running all the summer with this battery in another CB750.
I don't know much about electrics, so this is what I've done.
- Checked that the three yellow wires from the alternator wires have continuity between them.
- Checked the gap at the regulator, it was OK
- Screwed and unscrewed the regulator screw to increase the charging current, but the highest I reached was 13v
What else can I check. I said that I don't know much about electrics, I have a polimeter, but every book that I read seems to be written in a language that I don't understand. Could anyone tell me what to check step-by-step? Is there anything on the alternator, rectifier and regulator that I could check. Thank you.


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Offline mazingerzeca

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Re: battery not charging
« Reply #1 on: October 03, 2014, 10:23:12 AM »
Thank you very much!
That is what I was exactly looking for, despite they say that "This fault-finding chart assumes that the user has knowledge of the basis of electricity". Let's see if I have it!
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Offline flybox1

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Re: battery not charging
« Reply #2 on: October 03, 2014, 10:25:55 AM »
have you attempted to clean your harness connections and service (gap) your v-reg?
its quite easy.
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'78 750K (F3 engine) PD42b's, Modified airbox w/K&N  filter, 40/110 jets, 1 needle shim, IMS@ 1 turn out. Kerker + Cone 18" QuietCore

Past Bikes
1974 550K0 (stock), 1973 CB350F (stock), 1983 Yamaha XS400K (POS)
77/78 cool 2 member #3
"Knowledge without mileage equals bullsh!t" - Henry Rollins

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Offline mazingerzeca

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Re: battery not charging
« Reply #3 on: October 15, 2014, 06:31:28 AM »
Hello.
Cleaned my harness connections, and changed the yellow connectors from the alternator to the wireharness. It seems to be that the problem was there. Now I have to adjust the regulator, which screw I turned in and out thinking that the problem was there. I have the charging rates for 3000, 4000 and 5000 rpm (about 14,5v), but they must be stated for a bike with the lights off, and my bike always has the lights on (american model). Do you know which are the charging rates for the CB750 K7 when the lights are on?
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Offline PeWe

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Re: battery not charging
« Reply #4 on: October 15, 2014, 01:21:53 PM »
TwoTired has explained the charging system in detail with step by step description in several threads. You cannot miss to sort it out.
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CB750 K6-76  970cc (Earlier 1005cc JMR Billet block on the shelf waiting for a comeback)
CB750 K2-75 Parts assembled to a stock K2

Updates of the CB750 K6 -1976
http://forums.sohc4.net/index.php/topic,180468.msg2092136.html#msg2092136
The billet block build thread
http://forums.sohc4.net/index.php/topic,49438.msg1863571.html#msg1863571
CB750 K2 -1975  build thread
http://forums.sohc4.net/index.php/topic,168243.msg1948381.html#msg1948381
K2 engine build thread. For a complete CB750 -75
http://forums.sohc4.net/index.php/topic,180088.msg2088008.html#msg2088008
Carb jetting, a long story Mikuni TMR32
http://forums.sohc4.net/index.php/topic,179479.msg2104967.html#msg2104967

Offline mazingerzeca

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Re: battery not charging
« Reply #5 on: October 15, 2014, 01:25:29 PM »
Thank you. I was thinking about dismantling the headlight to switch the light off, but the fuse option is better :-[. I will check the TwoTired threads.
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