Hans Freekit
Well-known Member
Ancient Dad.. I would also like to read the carb setup pdf please.
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CB125 K5 '76 - 1st weekend.
- Thread starter Hans Freekit
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Hans Freekit
Well-known Member
Hello again VHT friends,
Here's an update. It's been a crazy week. I've had plenty of time to work on the bike. But it's just been a Pandora's box of stripped screws, dodgy wiring, dyslexic poring over of wiring diagrams and 1000 yard stares.
The claim of the previous owner that it was working fine the last time he put it away in the garage - is laughable. An insane, crazy laugh that is coming from the basement accompanied by a nervous tik of the eye.
Only kidding, but it has been one job creates another five jobs - and I've got quite a few bits and pieces off the bike now - waiting for parts to put them back together.
The main 'oh no' moment was when I took the headlight dimmer / starter switch off the handlebars (right hand side).
I had been testing the wiring - seeing whats working and what isn't - trying to work out why the starter button and hi-beam headlight switch didn't have continuity.
So I took it off to look inside as I suspected it was broken. Straight away I see the YELLOW/RED wire is not connected to the starter button (should soldered to plate opposite the button). Then I also see the white wire is also unattached - which I know is the low beam wire - from the headlight selector part of the switch. So, fixable thinks I.
But then the loom pops out of the inside of the handlebar - with about an inch of loom - it had been cut! see pic.
"Oh, joy, another stripped screw to dig out" - was my first reaction. But on closer inspection it looks like I can save the switch - just needs a cleanup and some soldering.
It explains why the headlight only has one beam and why the starter button isn't working. But the cut cable leads me back to where the other end should be - nothing in the rest of the handlebar - so I follow into the headlight birds nest of wires.
I untangle it and find a loom of wires that look like it should be the collection of wires that goes to the switch. But something doesn't add up. The wires attached nay, decapitated - from the dimmer / starter switch at present are WHITE (low beam) - BLUE (hi-beam) - BROWN/BLUE (?) - and the YELLOW/RED (from the AC) for the starter. Right?
The wires I've got in my hand from the loom in the headlight bowl do not match up.. see photo below.
In this loom I have BLUE, WHITE, BROWN, BLACK, a YELLOW which is out of the loom and taped up and a WHITE/YELLOW which is also taped up. see photo. The loom then ends in a board similar to the one that's in the dimmer / starter switch (only fewer wires). ??
So maybe this is not the loom from the dimmer/ starter switch after all. ??
In the headlight bowl I see no evidence of the former loom at all!
I will share the wiring diagram here also - because I've been staring at it too long - and I'm dribbling out of the corner of my mouth - electrics is NOT my strong point.
If any of you can spot something I've missed I'd be super grateful.
The kettle is on.
..NB, does anyone know what these abbreviations mean? DY, SE?
Here's an update. It's been a crazy week. I've had plenty of time to work on the bike. But it's just been a Pandora's box of stripped screws, dodgy wiring, dyslexic poring over of wiring diagrams and 1000 yard stares.
The claim of the previous owner that it was working fine the last time he put it away in the garage - is laughable. An insane, crazy laugh that is coming from the basement accompanied by a nervous tik of the eye.
Only kidding, but it has been one job creates another five jobs - and I've got quite a few bits and pieces off the bike now - waiting for parts to put them back together.
The main 'oh no' moment was when I took the headlight dimmer / starter switch off the handlebars (right hand side).
I had been testing the wiring - seeing whats working and what isn't - trying to work out why the starter button and hi-beam headlight switch didn't have continuity.
So I took it off to look inside as I suspected it was broken. Straight away I see the YELLOW/RED wire is not connected to the starter button (should soldered to plate opposite the button). Then I also see the white wire is also unattached - which I know is the low beam wire - from the headlight selector part of the switch. So, fixable thinks I.
But then the loom pops out of the inside of the handlebar - with about an inch of loom - it had been cut! see pic.
"Oh, joy, another stripped screw to dig out" - was my first reaction. But on closer inspection it looks like I can save the switch - just needs a cleanup and some soldering.
It explains why the headlight only has one beam and why the starter button isn't working. But the cut cable leads me back to where the other end should be - nothing in the rest of the handlebar - so I follow into the headlight birds nest of wires.
I untangle it and find a loom of wires that look like it should be the collection of wires that goes to the switch. But something doesn't add up. The wires attached nay, decapitated - from the dimmer / starter switch at present are WHITE (low beam) - BLUE (hi-beam) - BROWN/BLUE (?) - and the YELLOW/RED (from the AC) for the starter. Right?
The wires I've got in my hand from the loom in the headlight bowl do not match up.. see photo below.
In this loom I have BLUE, WHITE, BROWN, BLACK, a YELLOW which is out of the loom and taped up and a WHITE/YELLOW which is also taped up. see photo. The loom then ends in a board similar to the one that's in the dimmer / starter switch (only fewer wires). ??
So maybe this is not the loom from the dimmer/ starter switch after all. ??
In the headlight bowl I see no evidence of the former loom at all!
I will share the wiring diagram here also - because I've been staring at it too long - and I'm dribbling out of the corner of my mouth - electrics is NOT my strong point.
If any of you can spot something I've missed I'd be super grateful.
The kettle is on.
..NB, does anyone know what these abbreviations mean? DY, SE?
DY = Dynamo (white wire coming from alternator)
SE = Selenium (Yellow wire to the selenium rectifier/alternator.
A common modification is just to tie these together and eliminate the switched component of this - when combined with a modern rec/reg unit. This improves the low speed charging. It looks like they may have been taped together?
That "board" also belongs in the switch. When you slide the switch over to Hi beam, it automatically connects the white/yel circuit described above to bring both phases of the alternator into the charging flow.
SE = Selenium (Yellow wire to the selenium rectifier/alternator.
A common modification is just to tie these together and eliminate the switched component of this - when combined with a modern rec/reg unit. This improves the low speed charging. It looks like they may have been taped together?
That "board" also belongs in the switch. When you slide the switch over to Hi beam, it automatically connects the white/yel circuit described above to bring both phases of the alternator into the charging flow.
Hans Freekit
Well-known Member
Ahhh, right. I knew they went to and from Alternator or AC - but now it makes sense. Thank you so much. I'm starting to see the light again, after a couple of days in the wiring doldrums. Cheers.
AndrewJK
Veteran Member
Hello,
The hearness modification described by EzPete will work with modern voltage regulators and will result in higher grounding current to dissipate energy from stator coils. With original selenium rectifier the charging voltage regulation was done only by balancing energy output and input.
Proper charging values for battery are specified with regards to lights off (one stator coil as energy source) and lights on (all coils as energy source) and engine rpm speed for charging current. You will find proper table in the FSM. If current load will be reduced or power generation will be higher (by replacing bulbs to LED or using all stator coils with lights off) the charging current at idle will be improved, but at higher rpm You will slowly boil Your battery. Please, check charging voltage for this matter.
The hearness modification described by EzPete will work with modern voltage regulators and will result in higher grounding current to dissipate energy from stator coils. With original selenium rectifier the charging voltage regulation was done only by balancing energy output and input.
Proper charging values for battery are specified with regards to lights off (one stator coil as energy source) and lights on (all coils as energy source) and engine rpm speed for charging current. You will find proper table in the FSM. If current load will be reduced or power generation will be higher (by replacing bulbs to LED or using all stator coils with lights off) the charging current at idle will be improved, but at higher rpm You will slowly boil Your battery. Please, check charging voltage for this matter.
Hans Freekit
Well-known Member
Noted. I think for now, because I'm a bit overwhelmed, I'm going to just keep going to slowly put it back as it was - the whole starter and its wiring just seem to have been chopped out / bypassed. I want to see why.
Is the starter buggered? Was it because the dimmer / starter switch had failed? I don't know. But it would be a good start to take it back to how it should be first. So I understand it (if possible with my pea-sized brain) like that.. and then move on to upgrades or modern parts for better running. Hope that makes sense.
Is the starter buggered? Was it because the dimmer / starter switch had failed? I don't know. But it would be a good start to take it back to how it should be first. So I understand it (if possible with my pea-sized brain) like that.. and then move on to upgrades or modern parts for better running. Hope that makes sense.
Hans Freekit
Well-known Member
Hello sir,There are versions with and without starter. All are 6V, so battery capacity combined with starter consumption results in small startup margin. As such there engine covers with slot for starter as well as covers without this slot. My bike (red) does not have starter. My brother's bike (gold) has starter from the factory.
The OFF switch is on key. The unit pointed by AncientDad is starter indeed.
Rubber gaskets for carbs expands while contacting modern fuels. Use hot water bath to shrink them to the original size. Otherwise bowl assembly will be tricky.
I just ordered some carb gaskets from ebay. They arrived but they are too big. You mentioned shrinking with hot water. Do you think that would work in this case? The original is on the left.
Tony Clifton
Veteran Member
Others here may say different but I have had zero success with aftermarket carb bowl gaskets, they are ALWAYS just slightly wrong in shape and impossible to keep properly in the groove when reassembling. Then they leak
I have not myself heard of shrinking gaskets with hot water, doesn't hurt to try I suppose. Please report back on that one
I have not myself heard of shrinking gaskets with hot water, doesn't hurt to try I suppose. Please report back on that one
Hans Freekit
Well-known Member
..I boiled one and then put in the oven for ten minutes. It shrunk about 2-5% in size. Very precise science going here you know. But it may have shrunk.. But it hath not shrunketh enough.
But if you needed one to tighten one up just a tad - it could be the way.
I've had my arm up the handlebars today. Cajoling a loom.
Which is the first time in my life I've used that sentence.
So, you know, I'm grateful.
But if you needed one to tighten one up just a tad - it could be the way.
I've had my arm up the handlebars today. Cajoling a loom.
Which is the first time in my life I've used that sentence.
So, you know, I'm grateful.
That's not going to work. Given the number of "CB125" models over the years, it's not surprising to find these packing sets mislabeled. You're looking for part number 16010-304-305 On that side of the pond, CMSNL and David Silver Spares both show them in stock (although less expensive at CMSNL)
Hans Freekit
Well-known Member
So, moderators, I have a question regarding turn signals. Do I have to keep posting on this thread? Or can I start a new one?
Hans Freekit
Well-known Member
So after thinking I've got the Lighting / Dimmer / Start switch sorted - I refit it on the bars. I now have low beam and high beam headlight.
I have replaced all the bulbs in the tachometer with the correct voltage as in the wiring diagram. I have replaced the fuse type bulb in the headlight. So I'm happy something now works.
But the turn signals still wont come on.
So I test continuity through the circuit, following the very informative those guys in Houston guide videos on youtube - that seems ok.
I test the lamps they are all good. I test the switch - it's good. I even check the new flasher relay I bought on one lamp and it flashes - so i know that the relay works.
But here's where it gets interesting..
To test the circuit ,the guy at those guys in Houston advises to jumper the Flasher relay to protect it - while doing the other tests. (Diagram no. 1)
When I do this and curiously turn on the key and try the headlight switch - BOOM - the turn signals on the left are flashing! Switch it over the right - they are flashing!
Exciting times.. there's even the turn signal bulb illuminated at the tachometer! The Holy Trinity of the turn signal circuit. Glowing like a warm fire.
So, I realise the real test will come when I re-connect the black and grey wires going into the flasher relay - as it should be.. (Diagram no. 2)
Turn key on - turn headlights to left at the switch - nothing. Not even illuminated.
No turn signal indicator at the tachometer. Boo.
Deflated liked a popped balloon.
Any idea why this would happen?
(The flasher is good I tested it. The bulbs all good. Turn light in tach works - only when flasher is jumped) I include a little diagram i made to try and figure it out..
I have replaced all the bulbs in the tachometer with the correct voltage as in the wiring diagram. I have replaced the fuse type bulb in the headlight. So I'm happy something now works.
But the turn signals still wont come on.
So I test continuity through the circuit, following the very informative those guys in Houston guide videos on youtube - that seems ok.
I test the lamps they are all good. I test the switch - it's good. I even check the new flasher relay I bought on one lamp and it flashes - so i know that the relay works.
But here's where it gets interesting..
To test the circuit ,the guy at those guys in Houston advises to jumper the Flasher relay to protect it - while doing the other tests. (Diagram no. 1)
When I do this and curiously turn on the key and try the headlight switch - BOOM - the turn signals on the left are flashing! Switch it over the right - they are flashing!
Exciting times.. there's even the turn signal bulb illuminated at the tachometer! The Holy Trinity of the turn signal circuit. Glowing like a warm fire.
So, I realise the real test will come when I re-connect the black and grey wires going into the flasher relay - as it should be.. (Diagram no. 2)
Turn key on - turn headlights to left at the switch - nothing. Not even illuminated.
No turn signal indicator at the tachometer. Boo.
Deflated liked a popped balloon.
Any idea why this would happen?
(The flasher is good I tested it. The bulbs all good. Turn light in tach works - only when flasher is jumped) I include a little diagram i made to try and figure it out..
Your current Projects and Builds thread encompasses everything you do on your bike project.
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There is no real purpose to “jump the flasher to protect it” god, the unnecessary “hacks” in those videos have probably led to more dead bikes and rotting projects than anything else.
Do not overcomplicate this.
Switched 12v hot runs to the flasher (black)
Grey comes out of the flasher and to the left switch
Orange and light blue go out from the switch to their respective sides.
Signals and bulbs are grounded
One of your bulbs isn’t grounded on the side that’s not flashing,
Do not overcomplicate this.
Switched 12v hot runs to the flasher (black)
Grey comes out of the flasher and to the left switch
Orange and light blue go out from the switch to their respective sides.
Signals and bulbs are grounded
One of your bulbs isn’t grounded on the side that’s not flashing,
RobMan
Veteran Member
I had to run dedicated grounds from my rear turn signal housings directly to the frame to get them flashing properly. The stock grounding schema on these bikes is substandard at best.
Hans Freekit
Well-known Member
..Cheers for that. Mine is a 6v battery. I will check all the grounds very thoroughly.
..sounds like I might be doing the same very soon, merci beaucoup.
Hans Freekit
Well-known Member
I checked the ohm resistance on each turn signal lamp - All gave readings over 1. (1.2 to 1.6) So this means I have to find better grounds? Right?
What points were you measuring resistance from? That’s not ideal resistance but it’s not crazy.
Another complicating factor is we have no idea if you’re operating with factory signals or not. Assuming that you are, it may be as simple as just cleaning up the bullet connects for those grounds. Should be a shared 4-way female bullet around the taillight/rear fender with a bunch of green wires.
Also verify positive voltage at the bulb and that nobody put a 12v bulb in that signal.
Tony Clifton
Veteran Member
Any situation that invokes suspicious grounds, running a large wire directly to the battery for testing is a good idea
Sufficient (or insufficient) current gets all the press because it has a better publicist, but my experiences with Honda lighting (and cars!) often reveals grounding issues
Sufficient (or insufficient) current gets all the press because it has a better publicist, but my experiences with Honda lighting (and cars!) often reveals grounding issues
Hans Freekit
Well-known Member
All factory lamps. I was measuring from the black pos at the rear fender to ground screw on lamp. All 6v bulbs. Will clean contacts tomorrow. Thank you for your advice.
AndrewJK
Veteran Member
Hello John, rubber gasket boilign bath is working with gaskets which are enlarged due to contact with fuel (alcohol content improve penetration). If the gasket is new and dry there should be no significant size reduction.
Sorry for late reply, I was out of comp.
Hans Freekit
Well-known Member
Ha!, my name is Dave! ..no, it didn't work. I'm going to have to order the expensive ones from CSMNL. "Buy cheap - buy twice" I should know better really. ...
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Check David Silver Spares as well.
Hans Freekit
Well-known Member
OMG! I am so sick of this bike. What a lemon. Nothing works as it should. NOTHING!. Almost get the flasher working - following instructions - then it blows - then the headlight stops working - ARGH! what a ******* waste of time.
Hans Freekit
Well-known Member
I have had it.
RobMan
Veteran Member
Wiring problems can be maddening and the worse part is the fix is usually something very simple which is why most mechanics want nothing to do with them. Spend 2 days troubleshooting a problem and then try to justify the bill to your customer when it was a bad ground, a corroded connector or where a PO had "fixed" a problem.
Hans Freekit
Well-known Member
You are correct it was the main fuse. What I did do after I had calmed down, was take the new modern flasher and throw it up the garden. I got the original flasher. 50 year old flasher. Tested it - I can hear it clicking - which is more than the new ever did. Decided to try it - now that I’ve check all the connections in the circuit over the last few days and sorted the headlight bucket for good connections following wiring diagram - … as I’m hooking it up I’m curious about the grey and black wires. I follow them inside the frame and there are two more connectors there looking pretty grubby, I undo them and the black bullet point was completely corroded and white and powdery. ****! That’s it. Bingo Bongo.
I clean it up.
Hook up the old flasher.
Cross the fingers
Turn the key. Flick the switch …
WORKING! They flash!
Oh the drama.
I clean it up.
Hook up the old flasher.
Cross the fingers
Turn the key. Flick the switch …
WORKING! They flash!
Oh the drama.
Hans Freekit
Well-known Member
…cut to me looking the other flasher In The garden. It prolly works now. 
Hans Freekit
Well-known Member
Lemon Update:
So I think I've sorted the indicators and the niggly wiring and switch stuff. So I'm moving on. - I've got two things to do before I can attempt a start.
1) Put the cleaned and serviced carbs back on. I will need to check how long each piece of fuel line is and cut new sections - (I have new fuel line) - then fuel tank back on and hook it up - (with new petcock). One of things that had me thinking was how does the throttle cable route under the fuel tank? Left side? Right side? I'll probably look at the photos i took when i got the bike. See if I can see where it emerges.
2) I have an electric starter (this being the French CB125 K5 twin with starter) it was disconnected when I got the bike - so now the question will be should I try to start it with the starter for the first start - or should I use the kickstarter? The thing that bothers me about that is - I've not had the starter off to check it - it may be ****** - Also I've not had the left crankcase cover off yet either - to check the condition of the starter chain / sprocket.
I'm eager to try and start the bugger now that I've addressed the dodgy wiring / installed a new battery / replaced the handlebar Start and Dimmer switch - it might just go off all sweet and beautiful. First time. ..
OR..
I might wish that I had done option number two. Properly. Like a grown up.
What would you do?
So I think I've sorted the indicators and the niggly wiring and switch stuff. So I'm moving on. - I've got two things to do before I can attempt a start.
1) Put the cleaned and serviced carbs back on. I will need to check how long each piece of fuel line is and cut new sections - (I have new fuel line) - then fuel tank back on and hook it up - (with new petcock). One of things that had me thinking was how does the throttle cable route under the fuel tank? Left side? Right side? I'll probably look at the photos i took when i got the bike. See if I can see where it emerges.
2) I have an electric starter (this being the French CB125 K5 twin with starter) it was disconnected when I got the bike - so now the question will be should I try to start it with the starter for the first start - or should I use the kickstarter? The thing that bothers me about that is - I've not had the starter off to check it - it may be ****** - Also I've not had the left crankcase cover off yet either - to check the condition of the starter chain / sprocket.
I'm eager to try and start the bugger now that I've addressed the dodgy wiring / installed a new battery / replaced the handlebar Start and Dimmer switch - it might just go off all sweet and beautiful. First time. ..
OR..
I might wish that I had done option number two. Properly. Like a grown up.
What would you do?
Your starter cable was disconnected because the red/yellow wire in the switch was likely grounding on the handle bars and running the starter all the time. If it was me, I would try the electric start to see if turns over and also if the clutch on the starter sprocket functions properly. If you hear strange noise when operating the starter then disassemble and check the parts.
Hook the carbs up and hit the starter button. If it works, great - if it doesn't, kick it.
A good rule to follow for cables is long slow bends, which is easiest to accomplish when you cross the headtube - there's more range of motion for the cable to flex while turning. Sometimes you have to play around with it a bit if there's different bars, aftermarket cables, etc.
A good rule to follow for cables is long slow bends, which is easiest to accomplish when you cross the headtube - there's more range of motion for the cable to flex while turning. Sometimes you have to play around with it a bit if there's different bars, aftermarket cables, etc.
Hans Freekit
Well-known Member
..thank you Boddy. I think you're right there. Sage advice. - (Also I like the front suspension boots on your bike - are they aftermarket?)
Hans Freekit
Well-known Member
Yay!
They are the original boots from 1971, still in decent shape.
AndrewJK
Veteran Member
Hello Dave,
concerning throttle cable, please, note, that throttle cable is splitted for two separate carbs. It is slightly assymetric. Longer end goes to the right carb slider. It runs from steering wheel throttle through cable holder on steering wheel to maintain minimal cable bending. Then it goes back on the left side of the frame. Cable routing (throttle and front brake) is shown in manual.
I would try to test starter from the battery (if insulation is good and there is continuity on coils. For kickstarting do not pull clutch. Engine will run faster if You will try start this without a kick, by selecting second gear and using momentum to start the motor.