Topic: 81 CB650 Custom Charging System

[FortWayne650Custom]

Hi everyone, I'm new to the forum but after looking for a few days it jas already been helpful. So it seems that the old 650 customs all differ charging problems. Mine personally will charge at 13.5v at 2000rpm and 14.5v at 2500rpm and discharge when idling below that. So my question firstly is, why would Honda set the factory idle at 1500 if the bikes stator won't charge? And since my bike will charge some at 2000rpm would it hurt to bump the idle up a bit, just to keep the battery running when I'm cruising through stop and go traffic. Also since my stator seems to slowly drain my battery, has anyone considered installing a ground disconnect switch for when you don't have access to a battery tender? Sorry about the long post but had a few questions I was curious about.

[mono]

they'll probably move this to "Other Bikes" since i think the 81 650C is a DOHC - at least the one in my garage seems to be -- but (and i haven't read the 650C manual):

- if you're getting low voltage, you'll want to clean the contacts for the wiring if you already haven't, just to make sure you've got optimum contact.  also, at least with the older bikes, the charging system produces optimal power at a much higher RPM than idle (my 550 puts out optimal, yet still not enough, at over 5K RPM).  in otherwords, they're like sharks - they need to keep moving or they die lol.

i have heard that the early 80s Customs had a variety of problems with electrical components, too (no idea which ones) - so maybe another member can offer ideas there.

from what i hear, bumping the idle up is not recommended if you're riding in hot weather through stop+go traffic (air-cooled engine and whatnot).  from experience, i bumped the idle on my 550 to ~2000RPM for a while by advancing the timing slightly, and it did get kind of choppy on a hot day when i was stuck in traffic for about 10 mins, and i could really feel it kicking off the heat.  just my 2 cents on that.

[singedebile]

if its an '81 cb650 it is definitely a SOHC

[FortWayne650Custom]

That's what I figured as far as bumping idle up. I work 12hr shifts and the last thing I need is a dead battery, so has anyone tried the ground disconnect or any ideas to keep my battery from dying

[curemode2002]

I agree do not bump up the idle especially on the 650's they are prone to overheating if you are running to high an idle.

The ground disconnect is really only going to help a ton if you are loosing juice with the bike turned off and sitting.

I actually got 2 hours off of my battery only even with the headlight on. How much stop and go are you hitting? Do you get up to speeds that you can keep your RPM's in the 3000 range? I had a bit of a shock moving from a CX500 to the 650 you want to keep the RPM's high crusing around and remember they spool up to 10K.

For some great info on the charging system and how to optomize/troubleshoot take a look at the two following threads tons of great stuff for 650 owners.

http://forums.sohc4.net/index.php?topic=42826.0
http://forums.sohc4.net/index.php?topic=90327.0

[fmctm1sw]

Hi everyone, I'm new to the forum but after looking for a few days it jas already been helpful. So it seems that the old 650 customs all differ charging problems. Mine personally will charge at 13.5v at 2000rpm and 14.5v at 2500rpm and discharge when idling below that. So my question firstly is, why would Honda set the factory idle at 1500 if the bikes stator won't charge? And since my bike will charge some at 2000rpm would it hurt to bump the idle up a bit, just to keep the battery running when I'm cruising through stop and go traffic. Also since my stator seems to slowly drain my battery, has anyone considered installing a ground disconnect switch for when you don't have access to a battery tender? Sorry about the long post but had a few questions I was curious about.

Even 1500 RPMs sounds too high to me.  I'm thinking the 650 was around 1000      I'd imagine it would be hard on the transmission idling that high.

[F16Viper68]

I used the flowchart in the link below to chase down the charging issue on my 1981 650C (SOHC).   .

http://www.electrosport.com/media/pdf/fault-finding-diagram.pdf

Dave...

[trueblue]

It sounds like your charging system is working fine, I have a motobatt AGM battery in my 79 650 and I have never put a battery tender on it in 15 months, and have never had a problem with running the battery down while driving, I go out to the shed and press the button and away it goes even if it sits for a month.  The best thing to do when riding is let the engine rev, they love revs, my 650 doesn't really wake up until it hits 6000rpm and really sings a nice song above 8000rpm but when I ride around in town I keep it around 4k, if it is lower than that I just down shift.  Just don't lug the engine, it isn't like a car engine, putting a heavy load on these engines at low rpm will kill them a lot faster than running them at 8000rpm all day.

[FortWayne650Custom]

Yeah for some reason I'm losing about .5v over the course of two to three hours. Everythings working and I cant find what is pulling juice from the battery.

[trueblue]

Sounds like it is possible that you have a crook diode in your rectifier and it is letting some power back through your stator.

[scottly]

Yeah for some reason I'm losing about .5v over the course of two to three hours. Everythings working and I cant find what is pulling juice from the battery.

What is the battery voltage after sitting for 3 hours? If it's around 12 1/2 volts, you may not have a problem at all...

[grasscutter]

Yeah for some reason I'm losing about .5v over the course of two to three hours. Everythings working and I cant find what is pulling juice from the battery.

What is the battery voltage after sitting for 3 hours? If it's around 12 1/2 volts, you may not have a problem at all...

+1.

Stop!  Don't do all the 'bump up the idle'.  Leave it alone.  It all charging components are operating normally, that's the way honda made it.  Weird...yes.
Failure...no!  Been riding my 650 for over 17yrs.  Never have it on trickle (except in winter).  Stop and go traffic is fine. 

Stop sweating the small stuff.

[FortWayne650Custom]

Cool that's what I've been trying to figure out. I javent dealt with the older hondas much just getting into them and found some quirky things pop up.

[fmctm1sw]

Cool that's what I've been trying to figure out. I javent dealt with the older hondas much just getting into them and found some quirky things pop up.

BTW, idle says 1050 +/- 150 in the manual.

[Bodi]

Unless there's something wrong, you will have zero battery drain current when  the ignition is off.
The only components connected to the battery with ignition off are the starter solenoid and the rectifier. The starter solenoid might be corroded and passing a bit of current. The rectifier might be bad and passing current. Everything else is switched off by the ignition switch. The ignition switch might be corroded and letting some power through even when off. 
Any "off" current through the rotor would be leaking through a bad rectifier.
The alternator doesn't make enough power at <2000 RPM to have any surplus for charging the battery. This is normal. Even stop/go riding should have the engine running fast enough to charge a lot of the time, with an air cooled engine we don't have the option of endless idling.  Avoiding electric start if you're mostly in that kind of riding is a good idea, so you don't discharge the battery much before departing.
There are a lot of posts here about charging problems. The cause of deteriorating charge ability is usually dirty corroded harness connectors: just clean them all. I think yours has the powered rotor with brushes, if so check and clean the brushes and rings. For the passive rotor the bullet connectors and the engine plug can become dirty and reduce the field coil power, this reduces the alternator output.

[curemode2002]

+1 Bodi
any time I have seen a draw it has been those few things I had to really clean my connections and switches to resolve my draw when off.

[FortWayne650Custom]

Alright after a quick check the bikes been sitting at 12.5v for a few hours now after cleaning every connection. I'm getting 15v at 5000 rpm but 14.5v under that. Symptom of a bad R/R?

[curemode2002]

If the charging systems are working correctly that is what I would expect to see. So charging system wise I would say you are spot on.

What does that battery show right off a charger? A good battery for the 650 should show 12.6-13.6 that one sounds like it may be a bit low on fluid.

[FortWayne650Custom]

It's a brand new battery filled and installed at a local Honda dealer. It reads 12.8 right off the charger and will go down to 12.5v after sitting for a couple hours.

[curemode2002]

Yup definitely a bit of a draw there. My big issue was my stupid ignition switch it was all gummed up I bought a NOS switch and that made a big difference. The problem with those little draws especially with the 650's is they can be the stuff Brodi mentioned.

Very first clean the connections really good, I pulled my old switch and tried to clean it but no go, there are a ton of connectors that can hurt ya.

[TwoTired]

It's a brand new battery filled and installed at a local Honda dealer. It reads 12.8 right off the charger and will go down to 12.5v after sitting for a couple hours.

It may well do this even if connected to nothing, as it loses it's surcharge, and distributes its chemicals about internally.  Do you have an ammeter?  With the key off, insert the ammeter between either of the terminals and it's cable.  If there is a drain, the ammeter will show and give a magnitude.

Normally, it would be a few milliamps, (for rectifier diode leakage).  A bad diode would increase such a standing drain significantly.

15V is on the border of acceptance.  But, don't suspect the regulator until you verify it is getting an accurate report of true battery voltage.

The regulator's sense terminals should be very nearly the same as what appears at the battery terminals.  If there is pathway loss between those points, the regulator cant perform as required.   If the regulator "thinks" the battery is a volt lower than it actually is, it will tell the alternator to continue to charge it.  There other issue with voltage los, is that the regulator passes what it gets to the Field coil in the alternator to make a magnetic field.  Low voltage make the magnetic field weak, thus the output capability, as well.  This means at idle, when the alternator is trying to keep up with demand, it is being starved, and can't make as much power as it could, allowing the battery to deplete faster.

Cheers,

[trueblue]

+1 to everything TT said except I would say 15v was too  high, I would like to see it no higher than 14.4v, my 650 runs at around 14.2v.  Check the voltage at the black wire into the regulator if it isn't the same as your battery voltage then you have a bad connection somewhere.

Avoiding electric start if you're mostly in that kind of riding is a good idea, so you don't discharge the battery much before departing.

Only one problem with not using electric start Bodi, the 650 only has one way of starting it, and that is the electric starter.