Topic: Electrical Issues...with schematic

[thechris]

Hello again,

I posted awhile back about a problem I was having with getting all four cylinders to fire on my CB750. I changed the plugs and they've been working fine since. Thanks to all for their help on that issue.

Now a new one.
I had my bike running after I got it all put back together. It started with the key every time (for the first day) and I took it out a few times. The next day, I wanted to go for a little ride and she was completely dead. I checked the battery and it was drained. I charged the battery and I hooked up my multimeter. There was a drain on the battery of about a tenth of a volt every second! Something was really eating up this poor battery.

I thought that maybe something was grounding out. I've only got two wires coming off the battery. One that connects to the start solenoid and the other goes into the electronics box and splits to the key and regulator/rectifier. I traced the problem to the wire going to the elec. box. It seemed that when I disconnected yellow/red wire the drain stopped. But this is only a 16 or so gauge wire. I didn't think it would have the capacity to drain a battery that quickly and the wire isn't even warm.

Also, even when the battery was draining, I was able to get it started and as long as I kept it running, the battery held up. However, now the bike will barely run without a charger. The alternator can't keep up with the drain it seems.

Anyway, it appears there's more to this problem than what it seems. I made a schematic for the bike before I took it apart. Keep in mind, i'm not a master mechanic. Someone else wired this bike for me and it ran fine. I took it apart and made notes as to where every wire went and assembled it exactly as it was. Now i'm having a few people telling me this schematic looks wrong (including the guy who did the wiring!).

So, I figured I'd post it up here and see if anybody saw something that stuck out to them that would cause these kinds of issues.

Thanks!

ps- You'll notice this is not even close to stock. I'm basically running the bare essentials to make the thing work.

[thechris]

I don't know why, but the schematic looks like crap on my sceen. Here's the direct link:

http://www.noahs-hope.com/pos_schem4.jpg

[DRam]

You have a short circuit somewhere.  Does the yellow/red wire come from the electrical box (fuse box, one assumes) and run to the starter solenoid?  The only yellow/red I see is the negative lead to your starter solenoid.  If it does go to your starter, disconnect both the yellow/red and green/red wires.  You should have continuity between those two terminals, but none to ground from either.  If you do you have a shorted solenoid coil and need to replace it.

If, on the other hand, the yellow/red wire is the main feed to your fuse box you need to check each circuit separately to find out where your short is. 

[ct_racer]

I am not sure on the 750 but I do know that the yellow red wire on the 500 is the starter switch wire...  so if you unplugged that or whatever it could be what is causing your real drain problem...

[Bodi]

First, you should have a fuse before the ignition switch. The only unfused connections should be to the solenoid stud and the reg/rect red wire (you show red/white I think). I would go from the battery straight to a 15 amp fuse feeding the ignition switch. The switched ignition power goes back to the fusebox and gets distributed to the various loads through their fuses. Honda has the ignition powered direct from the (fused with a 15A fuse) switch and the other loads through lower (7A) fuses, this is a pretty good system. The problem is that if something in the wiring to the switch shorts out, you have a fire. The wire to the solenoid is heavy, stiff, and well insulated plus it can actually carry full battery current and probably not catch fire before the battery discharges. The original wire to the rectifier is a special thick insulation type with an extra insulating sleeve, and is very short with no flex points.
Your 30A fuse is way too big, unless you've used 10 gauge wire. The normal harness wire will be melted long before a 30A fuse would blow. A 20A fuse is also too big for the standard harness wire but I don't know what wire you've used, 14ga would be my minimum for a 20A fuse and 12ga the better choice. There's no benefit in overfusing - the fuse is for protection and an ignition system that takes 10A doesn't need a 20A fuse.
Anyway, your discharging problem. The regulator has two power leads, you show red/white and grey. The grey wire is the voltage sensing connection and control power to the regulator electronics, and it has to be switched. With the connection you show - the grey wire connected to battery "+" - the regulator will be trying to regulate the alternator voltage with the ignition switch OFF and the motor not running... putting a lot of power into the field coil plus whatever the electronics uses. Connect the grey wire to IGN power and you'll be good.
But for safety please straighten out the fusing.
I don't think the solenoid coil has any particular polarity, but if it doesn't work swap the two small wires... you have them connected reversed from Honda's way.
<edit> I didn't read the fuses properly at first I think. You show the Dyna with a 10A fuse - if you have 3 ohm coils this is too small a fuse, 15A would be ideal. The other sizes don't really make any sense so they may be mislabelled?

[Bodi]

This is what I'm suggesting, anyway:

[thechris]

Thanks everyone.
I knew something had to be wrong. As I mentioned, I didn't do the original wiring. I had another guy do that. Because it was not stock, perhaps he didn't know what he was getting into. 

As far as the fuses, I'm defintely going to change those. I just used what was put there before.

Also, I mis-typed my original post:
"I traced the problem to the wire going to the elec. box. It seemed that when I disconnected yellow/red wire the drain stopped. But this is only a 16 or so gauge wire. I didn't think it would have the capacity to drain a battery that quickly and the wire isn't even warm."

What I meant to say was the Red/White wire, not Yellow/red. Sorry about any confusion. Hopefully, the rewiring that Bodi mentioned will help this problem.

For the wiring, I believe I used 14 or 16 ga. All except the wire from the battery to the solenoid (8 ga.) and the wire from the battery that splices into three in the elec. box (10 ga.). I think I used something a little beefier to the fuse box as well. However, I cannot remember the gauge.

It does suck to have to go back to wiring. I spent a lot of time trying to get this thing right. But, I'd rather do it again (the right way) and not see my work go up in flames!

[thechris]

Bodi,
I was looking closer at your schematic.
For the wires from the elec. ignition. Two should go to the coils. That I understand. But, should the third be going back into the IGN circuit?

As I see, power is going to the start switch thru BAT. When the IGN is turned on, power is transferred to IGN. Which would power the coils AND if the Elec. ignition is spliced into that wire it would get power there also. Right? So where is the ground?
I thought maybe the coils grounded by mounting, but when the bike wasn't fully assembled before, the coils were taped to the down tubes. No grounding. And it worked. I don't see how this is possible.

[TwoTired]

Doesn't the Dyna make an electrical connection to where it mounts on the engine?  If so, that's the current path for powering the coils.

[Bodi]

The power to the coils is for the coils, to make the spark. The power to the Dyna plate powers the Dyna electronics that control the spark timing. Both circuits ground to the engine at the plate.

[750K2]

i may have missed if you mentioned how old your battery was.  old batteries can self-discharge as the lead sulfite collects at the bottom of the plates and can effectively short themselves out and discharge fairly quickly.  i'd also invest in a device known as an amp clamp which clips around a wire and measures current passing along the circut.  it's invaluable for quick diagnosis.  you can go through your entire harness in a matter of minutes.
frank