Author Topic: CB125s "Big Blue" is UN-DONE! (Read 57390 times)

Flying J · « **Reply #25 on:** May 24, 2011, 11:01:12 PM »

Wired up the LED light i used to run on my cb750. Boy is it bright compared to the old taillight.
http://s58.photobucket.com/albums/g276/thepanman99/CB125/?action=view&current=VIDEO0005.mp4

Flying J · « **Reply #26 on:** May 24, 2011, 11:19:18 PM »

ANybody have an idea of what size battery i should run. 12 volt bikes with starters run 9-12 amp hours but this is kick only. The 1984 cb125 had a battery that was 2.5 amp hours. If it was good enough for that bike i guess it should be good enough for mine. Any input?

Flying J · « **Reply #27 on:** May 25, 2011, 08:58:38 AM »

Well tryed to check the voltage and my regulator is not working right. Not sure if i have it hooked up correct. But i looks like the stator can turn out over 19 volts. At least that is what showed up on my meter at one point. Who knows im no electrical genius.

Coyote13 · « **Reply #28 on:** May 25, 2011, 09:15:11 AM »

Looks like you're just moving right along! Wish I had a little more knowledge in the electrical department to help you out, but I don't. What's that LED you're running there? May have to pick a couple up, I've been looking for replacements

Flying J · « **Reply #29 on:** May 25, 2011, 09:34:18 AM »

The LED is a sport bike LED i picked up off ebay.

Well i wasn't sure if the reg/rec i bought was working right as it has 5 wires and the 350 only ran 4. So i put on a Rectifier from a 350 and the bike was cranking out 18 volts at idle. So i dont think that it is regulating the voltage much. So i guess i go look for a 4 wire regulator/ rec?

kirkn · « **Reply #30 on:** May 25, 2011, 10:27:11 AM »

AC or DC?

The original CB125 was a 6-volt system that had a simple 4-wire rectifier - 2 AC wires in and 2 DC wires out. The 125 did not have ANY regulator at all. It was simply designed as a 'balanced' system - estimated output 'matched' to estimated demands.

The alternator can, indeed, churn out that kind of AC voltage. But, by the time it's rectified to DC, including losses, it's down where it needs to be.

**EDIT** Nevermind - I re-read the thread and see your 12-volt conversion efforts.

So, the 350's had a 4-wire rectifier (same design as 6-volt) and a separate 3-wire regulator. The rectifier did just that - rectified AC to DC - no voltage regulation at all.

The 350's regulator had a green ground wire, a black 'system' wire that looked at the overall system voltage, and a yellow wire that tied into the alternator's yellow wire. If the 'system' voltage got too high, the regulator shunted part of the alternator's output (yellow wire) to ground (green).

If you don't have a separate regulator, the stator's output can indeed be pretty high, DC, into the battery.

Kirk

Flying J · « **Reply #31 on:** May 25, 2011, 01:13:05 PM »

Thanks for the reply. YOu confirmed what i figured out by looking at wiring diagrams from the CB350, cb125 and a cb200. Went to the junk yard and bought a regulator. Ill wire it up tonight and see how that works out. Im also using the original 350 rectifier.

Flying J · « **Reply #32 on:** May 25, 2011, 03:53:27 PM »

Wired up the regulator i got at the junk yard for $20.

Ran the bike and the white wire on the regulator was getting really hot. So I wired in a regulator of a CB750 and it works fine. 14.2 volts at idle (1700 rpm) and 15+ at 4000 rpm. Now i need to find a way to store all the new electronics. I want to change out the rectifier for one of those small square ones, that will save on some room.

Here is a good wire diagram on how the power should be running.

Flying J · « **Reply #33 on:** May 31, 2011, 05:09:07 PM »

OK i think i have the electronics somewhat sorted out. I have a new rectifier i need to put on. Also got these pics from pamco pete. Ill be testing his electronic Ign. on my bikes.

Flying J · « **Reply #34 on:** May 31, 2011, 08:54:27 PM »

I got home today after riding a total of maybe 6 miles and my battery was down to 6 volts. I unplugged the regulator and it brought the voltage up to 12v at idle. So i know the bike has plenty of output its just not being regulated correctly. I aslo got my new rectifier in the mail and put it on.

kirkn · « **Reply #35 on:** June 01, 2011, 03:10:57 AM »

In your post (reply #32), you mention using a regulator off a CB750.

If that's a SOHC CB750, that won't work - the CB750 uses a field coil to control stator output. The regulator varies the amount of current the field coil gets. Your machine has a permanent-magnet rotor, so there can be no varying the stator output, so the regulator shunts some of the excess to ground when voltage gets too high. Different principles and not interchangeable.

If that's a DOHC CB750, you may be OK - I'm not sure of which type of charging system they used - a field coil or a permanent magnet.

Flying J · « **Reply #36 on:** June 01, 2011, 06:52:09 AM »

It was a 78 cb750. Im learning a lot about electrical systems and i do now realize that the 750s charging system is totally different and not interchangeable.

Flying J · « **Reply #37 on:** June 24, 2011, 11:35:13 PM »

Well I put in a different regulator and it seems to be charging just fine. I also wired in two 1ohm. Resistors to the coil to bring that back to normal. Bike runs pretty good. Clutch slips a bit so I'm guessing it needs some new disks. The front brake is pretty much crap. Anybody ever get one of these to work right? I was going to try and switch it over to a cb550 caliper but it will require a custom hanger so I think ill take the easy way out and just swap it over to a drum brake.

jaguar · « **Reply #38 on:** June 25, 2011, 05:32:18 AM »

The mechanical disc is junk.

Hot set up would be a 350 drum or T500

kirkn · « **Reply #39 on:** June 25, 2011, 06:58:52 AM »

Naahhh, I disagree on the mechanical disk being junk. I've had two or three over the years, and they all worked great. No issues. I've had 'em apart, cleaned, greased and reassembled no issues.

For the effort to covert to a drum, you're better off just disassmbling, cleaning, lubing and reassembling the mechanical disk.

Just my two cents.

Kirk

Flying J · « **Reply #40 on:** June 25, 2011, 08:56:05 AM »

The problem is that most people say that they are junk, even when they do work. Now the effort is not a problem. I have the left fork leg for the drum setup and a drum wheel. I am going to be changing out the forks from a different bike anyway so while they are off getting rebuilt i can make the swap. What will piss me off is if i stick with the disk and it is a PIA and then i have to take it all apart to switch to the drum. Now jag you say a 350 drum? has this been done? I have a 350t on the side of my house but i thought the forks were a little wider.

Anyway, i think that i need to clean the brake pads. The forks leak and i bet they have fork oil on them and thats why its not grabbing very well.

jaguar · « **Reply #41 on:** June 25, 2011, 09:30:18 AM »

I would assume that they front of a 350 is wider then a 125 but probably not by much.

If not a CB175 might be an idea?
The 175 drum is smaller then the 160

Flying J · « **Reply #42 on:** June 25, 2011, 10:04:07 AM »

I really dont have much problem stopping on my CL125 with its front drum.

1974blaze · « **Reply #43 on:** June 25, 2011, 10:10:33 AM »

i have the mech disc on the '78 cb125s and it stops great. of course i weigh in at a whopping 150lb.

jaguar · « **Reply #44 on:** June 25, 2011, 10:33:54 AM »

I have a drum on my CL125 and its adequate for the bike.

Flying J · « **Reply #45 on:** June 25, 2011, 01:29:15 PM »

I think ill try and sort out the disk before i swap out anything. It just feels like the pads are oily now. Put a little paint on the tank i will be using and a side cover. I like the color. Its rattle can so it will eventualy get ruined by gas but for now it will work. Its going to get a white strip done the middle.

Flying J · « **Reply #46 on:** June 27, 2011, 08:22:27 PM »

Chopped up my cl exhaust. Need to figure out what to run for a muffler. I alos fussed with the disk brake and got it to work a lot better. It does work better then a drum but holy crap there are a lot of moving parts. I guess ill keep it.

Flying J · « **Reply #47 on:** June 28, 2011, 12:06:57 AM »

F the disk brake, what a piece of #$%*. Got it so that when i pulled the brake it actually stopped the bike but when i was riding home from a friends house the bike was bogging down so i pulled off the road and the front brake was smoking! the thing was locking up on the front wheel. I really want to switch to drum now. Its just so much less hassle.

Flying J · « **Reply #48 on:** June 28, 2011, 09:31:18 PM »

Ok so i am keeping the disk but im tossing the caliper. Found a guy who will make me a new caliper arm with a hydraulic caliper.

Flying J · « **Reply #49 on:** June 29, 2011, 05:02:22 PM »

Sent out the caliper today. I Had a steering damper lying around so i figured i would slap it on lola. Looks good to me.

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Author Topic: CB125s "Big Blue" is UN-DONE! (Read 57390 times)