Topic: 750 K2 Not Charging (Another one)

[The Lone Builder]

So I took my "new" bike out for her first decent run on Sunday. A 250km run on good (for Zimbabwe) roads which, at 0700 on Sunday morning, were empty. The weather had cooled a bit (Sat was 30 C), reducing my previous concerns about overheating, and I was happy I had put on all my leather kit.

So things were going great; I was able to cruise with revs at 3-4,000 with occasional increases to 5,000 - running in so don't wnat to go higher. Then at about 200km, the bike just died. Out of fuel I thought, but switching to reserve did nothing.

To cut a long story short, the battery was flat, with a capital F. It was reading 9.something volts. A new battery, brought by my bemused son was inserted and we made it home with no further problem. However the new battery voltage had dropped from 12+ to 9V. On the first part of the run I had my headlight on, but not on the second - so just tail and instrument lights.

I have a stock system with an aftermarket RR and Hondaman ignition. I have also fitted relays to save the key switch and the headlight switches.

My questions:

I'm currently going through the various algorithms to try to identify the problem but while doing so I discovered that my black wire - at the key switch is connected to earth! Is this right?

Everything works except the regulator and I think the problem may be a lack of earth. I have a RR combo fitted and mounted it on the battery box and the body is not earthed. I have connected the earth wire to the old regulator to the switch saving relay. Since the battery box is rubber mounted, do I need to earth the RR body some other way?

Thanks for thoughts and advice.

[TwoTired]

The stock wires harness uses black color code wire to route Power to the bike's components including the vreg. which the vreg uses to both monitor battery status and route onward to the alternator field coil.

Connecting it to frame ground ought to pop the main fuse as soon as you turn the key switch on.  At the very least, your vreg can't do it's job without getting 12v power.

Cheers,

[bryanj]

There should be a ground wire on the reg/rec so the body should not need to ground but I do know that even an instantaneous incorrect wiring to the solid state units will render them useless

[The Lone Builder]

Connecting it to frame ground ought to pop the main fuse as soon as you turn the key switch on.  At the very least, your vreg can't do it's job without getting 12v power.

That's what I thought, but when I connect that black wire to the frame/engine, my continuity buzzer goes off!  And everything still works!

Well not everything - the vreg doesn't, and maybe, as bryanj suggests, that's why! 

When I bypass the vreg, the battery charges, so my plan is to ground the vreg and see what happens. Then I need to investigate why that black is grounded and where.

Will keep you posted.

[bryanj]

If you are using a buzzer between the black and ground it may well show a circuit as power is going through things e.g . Coils, bulbs etc

[The Lone Builder]

I think I tracked down my problem to the neutral switch/indicator circuit.

When I remove the bulb from the holder, the black-ground connection is broken. Same if I break the green/red or black wires.

Now, correct me if I am wrong someone, but when the bike is in neutral, the circuit is complete - to light the bulb - so irrespective of whether the ignition is on or off, the black will be connected to earth through the LG/R wire.

But then the oil pressure light circuit is the same, no? But is doesn't seem to behave in the same manner. So I can leave that bulb in place, remove the neutral bulb and the black/ground connection is broken.     I'm confused!!

I've also discovered that the neutral switch is not working properly. It only turns off in 3rd (sometimes)/4th and 5th gear. It seem to stay permanently on in 1st and 2nd. Do I just need to pull it out, and lube it a bit, or is this indicative of a problem with teh gear selector drum?

Cheers

[Bodi]

With the key off, you should probably still have continuity between black and ground as, on bikes with no headlight switch, I think the instrument lights and maybe more (neutral light?) are "connecting" black to ground.
If your reg/rect unit does not have a green wire (which should provide its ground), then the case must be grounded - usually by bolting it to metal. A ground wire might solve the charging problem. It also needs a black wire, I would take it from your switch saver relay output to reduce voltage drop as much as possible.
Black is switched power on your bike. How did you connect this relay?

[PeWe]

Problem to use the stock charging system? Regulator + rectifier.

[seanbarney41]

Problem to use the stock charging system? Regulator + rectifier.

There is really no reason to not use the stock #$%* on a cb750 on the street...I don't tamper and have never had a dead battery...since 2008 hundreds of thousands of miles.  Everyone that posts up on here with charging probs has an aftermarket reg/rec.

[PeWe]

I have one regulator-rectifier I found cheap on Aliexpress. Half price compared with same units on eBay Europe.
I'll not use it since I have read so many posts here about problems

I have never had any charging problems that I could not adjust. Bad battery with one cell off only. That was a very cheap battery that did not get any charge wintertime. And when I charged it I used a simple charger that probably left more AC than DC since this was in the first half of the 80's.

I talked to a colleague about charging systems. His bike (Aprilia 1000) has electronic regulator that burns off the overvoltage. That's why that kind of unit becomes so hot and must have good cooling. Installing a low power headlamp not a good idea since the regulator must work harder burning more to not overcharge, but overheat instead.

The only update I can think about is the modified stock regulator that guys on the German forum do that will ensure voltage earlier, making it possible to cruise long time on low rpm. Stock setup need 4000-45000 rpm and more to charge battery.

I have found oil dipstick with lock and oil lines stock design. Both guys wrote in English and did a good job. I'm sure that there is no problem to contact the regulator guy. There are 2 that provide the regulator
http://www.cbfourclub.de/boerse/750.htm

*Elektronischer Laderegler für CB 750 Four*
Kein Auskochen mehr
Voller Ladestrom schon bei 2000 U/min
Maximale Ladespannung 13,9 V für Gelbatterien und Reinbleiakkus dringend erforderlich !!
Original Optik im alten orginalen Gehäuse eingegossen, daher absolut Feuchtesicher !!
Preise: Für Clubmitglieder 55 €, für Nichtclubmitglieder 75 € (im Tausch gegen alten Regler) jeweils zzgl. Versand.

Google Translate:
Electronic charge controller for CB 750 Four
No more cooking
Full charge current already at 2000 rpm
Maximum charging voltage 13.9 V for gel batteries and pure lead batteries urgently needed !!
Original optics cast in the old orginalen housing, therefore absolutely moisture-proof !!
Prices: For club members 55 €, for non-club members 75 € (in exchange for old controller) each plus shipping.

I hope that will not cause too much stress on the generator coils.
It is probably possible to pay extra for the stock regulator to modify since shipping to German can cost more than an old regulator cost in Germany. There are several sellers there that sells old CB750 parts. Most imported from USA I guess...as  UK sellers do too.

[The Lone Builder]

Bodi, that all makes sense. Although it wasn't originally that way, with my replacement handlebar switch, the pilot light, instrument lights and tail light are powered when the ignition is on. The RR does have a green wire, but it goes into the 6-way connector block with the yellows and the red. There are then separate black and white wires which connect straight to the original vreg wires.

Relay is connected as follows: black - in - from flasher unit (85); green to earth ((86); red from fuse (30); power out -black - to coils and headlights (87). You can see this in the pic I posted if you look carefully.

Why a new RR?  Well, in my youth - 2 years ago when I started this build seriously - I foolishly believed that newer was better  . I was also not so adept at testing things properly; my test of the rectifier suggested it was U/S, so I went modern.

Now I have more experience  and I now know two things:

• Modern is not necessarily better
• The extra money spent on original parts is usually well worth it in termsof fit, quality and time saved

So now with the black/ground issue solved, I'm going to ground the body of the RR and see if it works. I'll also recheck the original regulator and rectifier and if they work, I might just put them back. Fortunately the battery box I modified to take the new parts was a spare, so I still  have one.

Finish this quote "When I was a boy of 14, my father was so ignorant I could hardly stand to have the old man around. Now I'm 21 ......" (Hint, Mark Twain)

Thanks for input.

[The Lone Builder]

Haha, PeWe; nice translation - I'm all for no more cooking, so I'll be calling him immediately!! 

I see he also does rectifier upgrades. Have you used any of these personally?

I might just go that way.

[calj737]

Finish this quote "When I was a boy of 14, my father was so ignorant I could hardly stand to have the old man around. Now I'm 21 and astonished to see how much the Old Man has learned in 7 short years."

[TwoTired]

Do you know that the new regulator followed the same wire color code functional convention as Honda?

I've seen some that didn't.

Cheers,

[PeWe]

Haha, PeWe; nice translation - I'm all for no more cooking, so I'll be calling him immediately!! 

I see he also does rectifier upgrades. Have you used any of these personally?

I might just go that way.

No, not yet. My K6 work fine. But this kind of offer is tempting to order while still possible.

I have NOS CB750 parts coming my way right now I could not resist to order since they cost much less than other sellers. Parts soon not available. Found a cheap front wheel hub, 30€. So I had to add rim and spokes on a DSS order. Am I a horder?

[The Lone Builder]

No, not yet. My K6 work fine. But this kind of offer is tempting to order while still possible. He has none left now. But will have more available early next month

I have NOS CB750 parts coming my way right now I could not resist to order since they cost much less than other sellers. Parts soon not available. Found a cheap front wheel hub, 30€. So I had to add rim and spokes on a DSS order. Am I a horder? Ehhh? I wouldn't like to comment, but there are places you can go for help! 

[The Lone Builder]

Do you know that the new regulator followed the same wire color code functional convention as Honda?

I've seen some that didn't.

Cheers,

Well, it had black and white wires along with the rectifer wires (Yellow, green and red).

Anyways, yesterday I hooked up the original regulator and everything worked!! So I guess the new vreg must be fried.

Then I re-connected the orignal rectifier and everything was nearly on fire - went from neg current flow to pos as soon as I increased revs from idle (±1,000); voltage up to 16+; and charging current at 6-7A!  I didn't keep it on for long.

I opened up the regulator and think maybe the gaps are too wide/small and the contacts need cleaning. So that is today's task, and to make sure the vreg earth is solid - yesterday I only wired it temporarily.

[calj737]

Then I re-connected the orignal rectifier and everything was nearly on fire - went from neg current flow to pos as soon as I increased revs from idle (±1,000); voltage up to 16+; and charging current at 6-7A!  I didn't keep it on for long.

Pretty good indication that you have no battery reference for the Regulator. 

[TwoTired]

Have you twisted the vreg adjustment screw?  That's the adjustment for the max voltage cuttoff point.

When adjusted correctly, it will not let the voltage at it's sense terminals higher than 15 V under any conditions.

Cheers,

[The Lone Builder]

So I went out with the intention of testing every combination of 3 rectifiers and 2 regulators - I decided the vreg incorporated with the new RR was toast .

Things were not going too well until I suddenly thought that the car battery I was using to spare my bike battery was probably throwing everything off, being of much greater capacity - which was why I was using it - than a bike battery.

The result with teh bike's battery attached? Things improved immediately. The regulator from a K1 I have coupled with the new solid state rectifier seems to give the best results - I stopped short when I found a solution so didn't do the full set of 6 x 2 readings.

What I have now is:

                                 1000                     2000                     3000                40000                5000
Lights off   
Volts                             13                      13.9                       13.8                    13.8                 13.6
Amps                           -2                         1                            1.2                     0.8                   2.4!

Lights on   
Volts                             12.3                    13.5                       13.8                    13.6                 
Amps                           -6                         2.5                            2                     2

This isn't exactly as per factory manual, but I think it's OK; yes/no? The battery and rectfier are not stock whcih I guess makes a difference - guess being the operative word.

The main thing is I'm charging from 2000 rpm upwards even though I never reach teh magic firure of 14.5V

Grateful for any thoughts.

Sean

[bryanj]

you will only see 14.5 when the battery gets to full charge so hopefully you are OK

[TwoTired]

The main thing is I'm charging from 2000 rpm upwards even though I never reach teh magic firure of 14.5V

It is charging.  That's good.  THe test is for a known good, fully charged battery.  If your battery isn't fully charged (lead acid) it won't get to 14.5 until it is.  At a 2 amp charge rate, you might need ten hours or more to fully charge a depleted battery.

Cheers,

[The Lone Builder]

That's good to hear. It's a gel battery, if that makes any difference.

Now I'll just have to get out and ride it - fuel availability in Zim allowing! 

I'll let you know how it goes.

Thanks for all the help.

Sean

[bryanj]

The charging system on these old hondas is a bit vicious for a gel battery mate