Back with a CT110, electrical issue

[Epic_username]

Hello all,
Ive been away from Honda bikes for a while, apart from a short stint with a 75 XL100, put an 82 XR200R motor in it, (sold it to make room for a DR350) but this past weekend I picked up an 83 CT110. Apart from mirrors and the auxiliary fuel tank, all the parts are there. I wanted a cheap to insure (Under 111cc) bike for my 60km round trip commute.

Anyways, after getting it running, I noticed all of the bulbs were burnt out/not working. With the headlight switch in any position, I don't have any power at the headlight. At the battery and tail light socket, Im getting 11 volts at warm idle. I did not check what the output was above idle.

Currently going through a wiring diagram to figure out what to test next, but sounds to me like I may have a bad regulator/rectifier?

At this point, having to replace most/all the bulbs, the very old battery, and possibly the regulator/rectifier, could I look into doing a 12v conversion? Seems like the stator wouldn't mind...


Cheers, David

 

[Epic_username]

Here is the CT110, I think I can get most of that poor gray paintjob off with a pressure washer

 

[69ST]

Here is a wiring diagram that (as described) covers your 1983 model.

Here's the same image, copied from dratv:

I've worked on Honda electrics that were on-par with this, in terms of complexity. That said, it's all been custom stuff and I've never tried going through the electrical system of a CT110. IOW, you're pretty well on your own with this one. Best I can offer is some generalized info to help you begin the process.

If I'm reading the schematic correctly, this bike has a full-wave electrical system, meaning that everything is fed DC, from the battery...with full alternator output being fed to the battery, via bridge-diode rectifier. If your rectifier has failed, then I'd expect to see more than a fraction of one volt AC coming through to the battery. The surefire fix would be OEM, or at least stock-type, replacement parts. Otherwise, it'll boil down to finding someone who really knows their way around this electrical system, or trial & error testing.

As for converting to 12v, you've heard of "bench testing" and "bench racing", right? "Bench (desk?) daydreaming" sez that measuring alternator output, using a voltmeter (set to AC), across the two outputs will give a good indication. I'd want to see well above 12V by ~3000-4000rpm. If you see, say 20V by ~3500rpm and values in the 30-50VAC range at cruising rpm (5000-7000), a full-wave 12v reg/rec unit ought to do what you want. Then, there's a full set of bulbs, 12v battery and flasher relay to source...which opens the floodgates on 2018 technology.

Hopefully, I've not caused any migraines...

 

[Epic_username]

I figured as much, there isn't much room for a bigger battery in the CT110 compartment anyways...

If I'm looking at the schematic correctly, looks like the headlight gets power straight from the alternator so I'll have to check that too.

I haven't checked AC output at the battery, next time I'm near the bike I will.

Thanks for the input!

 

[69ST]

I don't think that battery dimensions will be a problem. 12V SLA batteries are available in a few different sizes; there's also such a thing as running dual batteries, parallel (+ to +, - to -) wired, That's a nice option to have, if needed. And, if the alternator has a floating ground, you may be in business. Full-wave reg/rec units require a floating ground stator, to work. IMO, your proposed 12v conversion may be one helluva lot easier than doing so with any of the 72cc bikes, except the CL70. FYI, I'm running a Honda Nice 110 motor, with the stator modded to a floating ground. Also using the OEM Honda Nice wire harness. The Nice (the bike) is, essentially, an updated CT110 with 12V/CDI electrics and aero-style fairings. The wiring is similar to the CT110/90 but is (was) a half-wave setup. I've been running a Trail tech reg/rec unit, which has a voltage adjustment, via trimpot. The Nice harness has a 4-wire keyswitch pigtail...which I'm using with a 7-wire CT70 (ST70, actually) keyswitch. It sounds more complicated than it really is...unless one lacks basic electrical knowledge. I think that your conversion may be waay easier than this.

 

[fatcaaat]

I've converted a ct110 to 12v. It wasn't worth it in the end, but I did. All I did was change out the reg/rectifier and added a second regulator and swapped the bulbs, blinker, and battery. Worked just fine, but didn't really improve anything. I could have simply added a 6v LED (make sure you use the ac versions or they will flicker) up front and out back and called it a day.

 

[Epic_username]

I think for simplicity's sake, I will try to repair the 6 volt system. I'm going out to the bike tonight, my multi-meter has a diode check function, hoping to test the regulator/rectifier

 

[69ST]

IMHO, the main benefit of 12v power is more bulb options. With 12vDC (a.k.a. full wave) you gain access to the world of LEDs, including headlights, and electronic controls such as flasher relays. They all outperform the old incandescent & mechanical flavored parts by a huge margin. The only HL I've seen on a small Honda, of this vintage, that seriously rivals current automotive light output has been LED. A 25W LED will outshine a 30W incandescent bulb by several orders of magnitude...and run at least 100 degrees cooler. Electronic flasher relays maintain a steady & reliable flash rate, regardless of circuit load. It comes down to whether any of that matters to you. 6vAC, as with 6v parts in genera,l is obsolete technology; it wasn't wonderful even 30+ years ago. That said, as long as the stock parts are still available, those are the simplest way to go. Direct replacement of components is far easier than any kind of electrical update/conversion...which is going to be a roll-your-own proposition, to some extent. The only person who can decide if it's worth venturing into is the one responsible for the bike.

 

[Epic_username]

I'll have to think on it, brighter lights would be nice...

So my DMM packed it in yesterday, I tested the rectifier with another analog multi meter, set to resistance. I don't remember exact numbers, but going one way all the diodes were the same, and the opposite way they all read open. So that part of it seems to work ok. Not sure why I'm getting 11 volts at idle, I can't think of what to check next.

Maybe the battery is so far gone that it's not absorbing ecxess voltage? Perhaps I have a bad ground somewhere?

 

[69ST]

Wish I could be more of real help with this. I've never so much as attempted to diagnose the electrical system in one of these bikes. FWIW, the current production bridge diode-electronic reg/rec unit I've been using requires a healthy battery, otherwise, it throws all of its toys out of the crib, i.e. flickering lights and low system voltage. Might be worth breaking out the charger to see if your existing battery can be revived, then doing a retest. It really sounds to like your rectifier diodes are still functional.

 

[Epic_username]

Well today is the first day this week I've been able to spend more than 10 minutes on this bike...

Started it up, and at a reasonable idle I still have 11 volts at idle. I switched the multi meter to AC voltage on a 50v scale, and if I'm reading it right, I'm getting ~25 volts A/C at the battery (I'll admit I'm not used to an analog multi meter)

Shut the bike off, removed the battery and let it sit for 10-15 minutes after idling for about 20, and it was right at 6 volts. Water/acid level slightly above the minimum, so sounds like the battery is ok. Grounds are ok, and I bypassed the ignition switch to be in the on position just to eliminate that possibility.

Might go to the used bike shop to see if I can match up a rectifier, if I can get there before they close

 

[69ST]

Anything above 13-14 volts should be enough to charge the battery and keep it charged. 25VAC seems like it'd be enough. The key is maintaining 12VDC+, at the battery and under load. Raw AC voltage varies wildly...falling-off at idle, then rising dramatically as rpm increases. My 12v engine makes 30VAC at an estimated 3500-4000rpm, with 50VAC seen at ~7000rpm and it's nothing special. Doesn't really matter if voltage falls below nominal battery voltage, at idle; that's the main reason for having a battery in the system. As long as it charges, once revved above idle, you're rolling.

I'd check battery voltage daily, over a week or so. That'll give you a better indication of its condition. Another way would be applying a known load, like a bulb, then monitoring voltage over a set time. You want to rule-out the possibility of the battery taking only a surface charge...a condition that's confused many of us, at one time or another.

 

[Epic_username]

I will continue to check the battery. But if that amount of AC voltage could in theory maintain a 12v system I'd have to get a 12v battery anyways... I'll go back out there tomorrow to see what voltage levels I have at higher rpm.

Perhaps in the past someone changed the stator out from a 12v bike? Not even sure what parts from what bike would be needed to do that. I should pull the left side cover and see if I can find any part numbers.

 

[Epic_username]

Come to think of it, I have an electronic 12v flasher unit left over from a Yamaha L5 project, with adjustable flash speed, one less thing to buy. I have in my toolbox at work a 12v battery that's roughly the same size as the original 6v, I think it's from an alarm system so I'd have to do some research to make sure it's compatible.

 

[Epic_username]

Well my 6 volt battery held a charge, but there's stomething wrong with the rectifier. With both the 6 volt battery, up at charge, and the 12 volt battery borrowed from my DR350, also charged, I was getting 11 volts DC at idle, and 30 volts DC at half throttle. The headlight coil was putting out 4 volts at idle (didn't check that at throttle) .

So I've got an overcharging condition. Since the rectifier isn't much of a regulator on these bikes I think I will look for an aftermarket regulator/rectifier combo, in either 6 or 12 volt, get a reliable alternator output, and go from there.

Racerx, you say your reg/rec has an adjustable voltage output?

 

[69ST]

Yes, the Trail Tech unit has trimpot voltage adjustment, as well as a time-delay that doesn't have to be used. FYI, you must have two AC inputs, from the same coil, or coil array and a floating ground to use this unit. Otherwise, you're asking for an endless nightmare of zero voltage output.

Here's a link to the unit I'm running. Here's the installation instructions. Do your homework before clicking the "add to cart" button.

 

[Epic_username]

Well a bit of an update. Just for giggles, I thought I'd try the 6v regulator/rectifier that the good doctor sells for putting 12 volt Chinese engines in a 6 volt bike. For the $16, I figured I didn't have much to lose.
http://dratv.com/6voregre.html

Well I hooked it up and tried a few different ways, but couldn't get it to work properly. I think this is due to the charge coil in the 1983 CT110. Both ends of the charge coil go to the original rectifier (I assume the body of the charge coil is ground?) With the 6 volt battery hooked up and holding charge, and the white/yellow wire from the charge coil going to the AC input on this reg/rec, and the pink wire from the charge coil left unhooked, I get no voltage output from the reg/rec. If I switch the white/yellow with the pink, no change. Same thing if I ground the pink wire with the white/yellow wire plugged in, and vice versa.

If I use the output from the headlight coil it works but I don't feel that's the right way to do it, also I only get 2 volts at idle and it doesn't stop at 6 volts (went right past 11) on throttle.

Is there a way I can take one end of the charge coil, and ground it? Like the lighting coil/a lifan charge coil? Stuff like this is outside my range of electrical knowledge. Perhaps there's a failure in my stator, like too much resistance or not enough, causing the charge coil to create too much voltage?

I'll have to find specs and ohm it out soon.

Cheers!