ehenry
join:2007-11-07
Fairbury, IL
| Battery not holding a charge? (1979 Honda CB750k)
I figured I had better start a different thread for this question.
My battery will charge fully and stay charged overnight. This tells me the battery is still good, its only about 2 months old. When installed on the bike and started the bike runs but once the bike is shut off the battery doesn't have enough juice to turn the motor again. I would like to test the connections between the components of the charging system.
I know the main components of the charging system is the rotor, regulator, and stator. My problem is that I don't know where this items are or how to test. I have looked for any pictures showing the locations of the items, but were unsuccessful. I have found a website that shows what the resistance should be.
I'm I headed in the right track? Is there anything else i'm missing? Can someone point my to a diagram of the charging system? Help needed.
**Dr. Olds--The mechanic says the carbs are synced. I'd rather not send the bike back to him if i can help it. Its getting rather expensive. Thanks. |
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sailor
Merry Whatever ..R.I.P. dadkins
Premium
join:2003-10-21
Long Island | Don't know if this will be helpful to you but here it is
»en.allexperts.com/q/Motorcycle-R···-won.htm |
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neonhomer
Honoray Mythbuster
Premium
join:2004-01-27
Edgewater, FL
clubs:
 ·Earthlink Cable Mo..
1 edit | reply to ehenry
First off, check the output to the battery. Fully charge the battery. Warm the bike up, and then while holding the throttle around 3000 rpm, check the voltage. Should be around 14.8 (IIRC).
There are three major parts to fail. Regulator, stator, and battery. Just because the battery is new, doesn't mean it isn't defective. I bought a battery for my 86 Honda VF700C and it lasted about three months before it died. Took it back and got a new one, and it lasted almost two years. Make sure you are using the right battery, with the right capacity.
Did you fill the battery yourself? Did you use water or electrolyte?
To check the stator, you have to unplug it from the regulator. Fully charge the battery, and then warm the bike up. (Use a battery charger to keep the battery charged if necessary.) Test across all three legs of the stator using the AC volts side of your multimeter. At 5000 RPM, should have about 80 volts or so. (Once again, IIRC... been a while since I tested one.)
Stator will run about $300 or so from Honda. Regulator about $150-200, and batteries are around $100. You can get regulators from J&P Cycle a little cheaper, but your best bet is to stick with genuine Honda parts.
Stator is physically located (usually) on the right side of the motor. Regulator can be in a number of places. My 83 Nighthawk had it below the left side cover. My friend's 94 Magna has it under the battery. You can find it by looking for a finned block with two wiring harnesses (or 7 wires) coming out of it. Should have three yellow wires, two reds, and two greens. Yellows are your stator feeds, red is battery positive, and green is ground.
EDIT: Locations
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"F is for Fire that burns down the whole town...
U is for Uranium...... Bombs...
N is for NO SURVIVORS!!!!!" Sheldon Plankton |
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Doctor Olds
I Need A Remedy For What's Ailing Me.
Premium,VIP
join:2001-04-19
1970 442 W30
clubs:
| reply to ehenry
said by ehenry  :I **Dr. Olds--The mechanic says the carbs are synced. I'd rather not send the bike back to him if i can help it. Its getting rather expensive. Thanks. If they are in sync, then they would have to had been to be synced on the bike while running and pulling vacuum so I ask why the idle wasn't set then when he did the synchronization???
If the battery dies overnight after a charging (normally should show 12.6 volts to 12.9 volts fully charged after load testing and letting sit) then there is a drain on the system that needs to be found. It could be a diode in the diode trio or it could be a drain elsewhere.
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What’s the point of owning a supercar if you can’t scare yourself stupid from time to time? |
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ehenry
join:2007-11-07
Fairbury, IL | reply to ehenry
The battery does stay charged overnight. Its only while the bike has ran for awhile does the battery die. |
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ehenry
join:2007-11-07
Fairbury, IL | reply to ehenry
Narrowed it down to the rotor and stator. The brushes are rusted and dirty. Is there a good way to clean these? |
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Doctor Olds
I Need A Remedy For What's Ailing Me.
Premium,VIP
join:2001-04-19
1970 442 W30
clubs:
| You might want to join a motorcycle forum for the detailed tips and tricks.
honda cb 750 restoration
»www.bikerforums.org/showthread.php?t=2066
said by jtrouten :
If you have the same electrical problems that happen to all these bikes you are gonna have to replace the rotor, stator, and reg/rectifier which is about $500 at the cheapest for all those. I have to do my wiring harness as well so I would check that if I were you. Carb rebuild, tune, and sync is gonna be at least $300 at a shop. Tires are gonna be around $200.
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What’s the point of owning a supercar if you can’t scare yourself stupid from time to time? |
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StNickless
@tmodns.net
| reply to ehenry
Most any electronics shop (Frys included) will stock 90% or higher isopropyl alcohol.
You don't need much, get the smallest bottle you can.
Do NOT use drug store 70% stuff, it will leave residue.
Old tooth brush.
Get busy and don't be shy....scrub the bejeezus out of the whole assembly.
It is very rare for a rotor or a stator to actually be bad, it's almost always a brush a rectifier or a diode.
Even if you have to buy a whole brush plate and a diode assembly I doubt you'll find it to be much more than about 100$
Just be careful and don't bend anything or tweak any wires (solder joints).
You can use a 220 grit sandpaper (good quality wet and dry) to clean the contact surface of the brushes. Be sure to keep the concave contact surface the same shape it is....so it fits.
No oil, no grease.
Clean and dry.
g'luck. |
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ehenry
join:2007-11-07
Fairbury, IL
| said by StNickless :
Most any electronics shop (Frys included) will stock 90% or higher isopropyl alcohol.
You don't need much, get the smallest bottle you can.
Do NOT use drug store 70% stuff, it will leave residue.
Old tooth brush.
Get busy and don't be shy....scrub the bejeezus out of the whole assembly.
It is very rare for a rotor or a stator to actually be bad, it's almost always a brush a rectifier or a diode.
Even if you have to buy a whole brush plate and a diode assembly I doubt you'll find it to be much more than about 100$
Just be careful and don't bend anything or tweak any wires (solder joints).
You can use a 220 grit sandpaper (good quality wet and dry) to clean the contact surface of the brushes. Be sure to keep the concave contact surface the same shape it is....so it fits.
No oil, no grease.
Clean and dry.
g'luck.
Hey thanks, that did it....Thanks all. |
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StNickless
@tmodns.net | Kewl, glad to be of help.
Also, thx for a closure post.....so many people don't do that. |
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