Topic: first ride: 1976 CB750F. now tuning / charging issues

[riffman12]

OK guys... I think you were right about the ignition switch.

Installed my new rec / reg combo and here are my RPM results:

1000: 12.2V

2000: 12.6V

3000: 13.1V

4000: 13.6V



So it looks like my issue is still there. Then I went and tested the ignition switch. Let me know if this is correct:


1) Key off, I put my black probe on the neg battery terminal, red probe on the red wire at the fuse box

2) Key to position 1, black probe on neg battery, red probe on black wire at fuse box

3) Key to position 2, black probe on neg battery, red probe on brown wire at fuse box



here's my results:

battery voltage ignition off: 12.6 V

battery voltage ignition on: 12.2 V

red wire at fuse box: 12.57 V

black wire at fuse box: 10.95 or 11.1 depending which side of the fuse box

brown wire at fuse box: zero



My position 3 has never actually done anything now that I think of it... What is it supposed to do?

Am I right in thinking the culprit is my ignition switch? What's my best plan of action here? Replace it or rebuild it?

[calj737]

From your results, I don't see the switch as being the issue.if I understand your tests/results correctly, the 10.95/11.1 on BLACK concerns me. But that begs the question of how/where you wired your Reg/Rec into the harness.

The BROWN having 0v may be a bad fuse. Test continuity across the fuse with your meter.

[riffman12]

hm but if I'm measuring 12 .2 across the battery and only ~11 through the switch, isn't that sucking up a lot of voltage?

The 3rd key position has never worked since I bought the bike. That plus the voltage drop makes me suspicious of the switch.

The fuse box is brand new from HondaMan so I don't think that's the issue.


Some of my measurements might be kinda odd because I'm new to all this wiring stuff and have no idea where to stick the meter probes haha. I stuck the red probe inside the plastic block connector where the fuse box connects to the harness...is that a good spot to test the switch? I'm not sure where else to test the wires coming out of it.

[calj737]

For the Brown wire, I am suspecting the actual fuse may be blown if you don't read voltage on it. Either that, or that entire circuit from the key is bad?

You said there's a Black wire at your fuse box? I'm not familiar with that configuration off the top of my head, so it's a bit confusing to me. Can you snap a picture of your fuse block and another of how/where you have the Reg/Rec connected?

[riffman12]

checked the fuse block. There is continuity across all 3 fuses.

Here's a pic of my fuse block. This is where I was sticking the red probe to test the ignition switch




Here's how the reg/rec combo is wired:




It plugs into the normal block connector that plugged into original rectifier. Then the 3 skinny wires plug into where the original regulator spade connectors did

[riffman12]

as a way to rule out the ignition switch, could I just remove / bypass it (hot wire the bike basically), and then do an RPM voltage test?

Then if my readings are good I know it's the switch, right?

[calj737]

You could use this diagram to ascertain the status and condition of your components:
http://www.electrosport.com/media/pdf/fault-finding-diagram.pdf

[riffman12]

ok thanks

the only part that I'm a little lost on is "Count the # of DIFFERENT wire COLORS coming from the RR."

My new reg/rec combo unit has a block connector as well as 3 separate wires. Do I go down the "4 or less" arrow saying that our bikes have a permanent magnet alternator system?

[calj737]

More than 4.

[Jerry Rxman Griffin aka MuthaF'er]

Yeah, your magnet is not permanent. It is made up of your stator and field coil and is only working when the crank is turning and there is voltage going to the field coil to 'excite the field'.

[riffman12]

hm well now I'm confused again. If I follow those directions it takes me to section "D"

If you follow from there, the only possible "end points" are a fault RR (which is brand new in my case) or a stator / rotor problem. It doesn't seem to point you toward any wiring problems or ignition switch circuit like in the other sections.

[calj737]

It should take you to testing the output of the stator (follow the path, Lower than 14.8v)

[riffman12]

OK this evening I will be following that guide. As I poke around at old threads I found this post:

The Dyna takes about 10 watts of power for its electronics and it has a very short dwell angle so both coils are on almost all the time, quite a lot more average load than the points system.
The alternator has very little extra power: with a dead stock bike and a healthy charging circuit it's only capable of charging the battery above 3000 RPM or so.
With the Dyna you can't also have a high wattage headlight or extra lighting. If you've put in an H4 headlight with a 50W+ lamp you're in trouble, the battery will never charge. You won't get stranded but you won't be using the electric start. You can get 35/35W bulbs that aren't as bright but still better than the feeble stock headlight.

Has anyone heard of this?

I have both an H4 bulb and (i believe) Dyna electronic ignition

[calj737]

If you think that's your problem, simply test it. Pull the headlight fuse, start your bike, and take voltage readings at the battery at 2,500, 3,500 and 4,500 RPMs. Compare that to your other readings.

I use a Dyna S on my bike, with H4, and get 14.7 at 4,800 RPMs. So you tell me whether it won't work?

[przjohn]

How did this go 3 pages? How about some method troubleshooting from square one.

[riffman12]

How did this go 3 pages? How about some method troubleshooting from square one.

I'm awful with electronics so it's been a learning experience. I will be method troubleshooting from here on out, but the last couple of days I've been trying to make sure all my connections are good.

Stupid question: last night i tested some voltages without my 55W H4 headlight on and obviously the numbers were higher.

When we test voltages at different RPM ranges on these bikes, should the headlight be on or off? or does it not make a difference?

[Jerry Rxman Griffin aka MuthaF'er]

Some of US can not turn off the headlight short of removing the bulb or fuse which is also an option when your battery is getting low and you're on a ride. That is just one way to see the draw of the bulb and the results with it off. Test with it on. Your voltage regulator should take care of the drop.

[riffman12]

Big thanks to calj737 and everyone else who gave me a hand with this.

I tested voltage drop at various components (ignition switch, headlight, left and right hand switches etc) and nothing seemed to be too big of an issue.

So yesterday I continued cleaning grounds and connections around the coils under the tank. I'm not sure which one it was exactly, but something must have worked because suddenly I was getting too much charge back to the battery

I gave Cal a call and he was nice enough to guide me through a few tests to figure out what was going on.

In the end, he had me wire the black from my reg/rec directly to my positive battery wire at my starter solenoid, bypassing any possible hangups in the 40 yr old harness.

Now the battery seems to be charging perfectly, at least on garage rev tests. This afternoon I'm going to take it for another ride and see how it goes. I'll report back.

Thanks again guys

[Jerry Rxman Griffin aka MuthaF'er]

Congrats to you AND Cal. Hard work rewards good results. Is a new harness in the works?

Ride and enjoy!!

[calj737]

Jerry - He cleaned all his connections so well, that his Reg/Rec is sending too much voltage to the battery. His harness only sees 0.5v from Key to harness-side black, which is pretty darn good. Problem is, that 0.5v is accounting for too high charge (15.1v) at battery.

Using the solenoid stud gave him almost exactly voltage from the Reg/Rec to battery as the Reg Black saw. He should  be able to run a 75/90w light now at idle!!!  (Kidding of course)

[Jerry Rxman Griffin aka MuthaF'er]

So what's your take on the regulator side?

I had forgotten I now have a jumper wire in my tool box rather than straight to the battery as you had him do. That's a good trick at times. Nothing a whole new wiring system won't fix LOL

[calj737]

Technically speaking he's going to the solenoid for metering of the battery voltage.

[riffman12]

so  I got some riding in today and the bike ran awesome. Smooth through the whole rpm range, pulls from all the way down low. Here's my plugs after some mixed riding. What do you guys think? I'll be doing a proper wide open plug chop later. Most of this was from 1/4 to 1/2 throttle.




closeup of #4:

[Jerry Rxman Griffin aka MuthaF'er]

Show off!

[calj737]

Show off!