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Blood Sweat Tears and Grease => Projects => Cafe Racers => Topic started by: vwrabbit on May 04, 2017, 21:54:20

Title: 1975 Honda CB125S
Post by: vwrabbit on May 04, 2017, 21:54:20
I've taken over ownership of my brother's old CB125. It's a '75 and when my brother got it back in the 90s, it was near mint. It's survived some stints off-road and at college while in his care.

Now that I have a garage and a little $, it's time to do what I've been wanting to ever since he got it. The plan is to build a cafe seat, clubman bars, convert all lights to LED and 12v. Replace the lollipop turn signals with something a little more modern, and maybe some rear sets.

Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 04, 2017, 21:59:43
Today I replaced the battery with a WPS 12v li-ion battery, a 12v regulator/rectifier and bodged an LED neutral light to verify the conversion worked. I also removed the battery tray, air box and toolbox.

Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 04, 2017, 22:04:47
Now I need to get the stock carb with new float back on. Can't get the bike with a Chinese carb to start. The original float was full of holes. Might also need to clean the points and check the valves. The bike ran two years ago and only had about 2700 miles on it.
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 04, 2017, 22:09:52
Once it's running, I plan to strip it down, clean it up maybe a repaint. If I can find a Benelli Mojave or CB160 tank cheap enough, I'll swap tanks.
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 09, 2017, 10:50:29
I replaced the Chinese carb with the stock and new float, added some more fuel and it starts but won't run for very long.  Need to double check timing.  It might be due to the fact the stock airbox has been removed...  Carb and jets were cleaned before reassembly.
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 09, 2017, 10:52:03
Also look to be missing the "caliper joint - 45104-107-720".  This mounts to the top of the caliper where the fender is bolted on, but my brother removed the fender a while back.  I have the fender, but don't seem to have the caliper joint.  Does anyone have one or know where I might find one?
Title: Re: 1975 Honda CB125S
Post by: crazypj on May 09, 2017, 12:48:02
The cable operated brake can be made to work OK but parts are very rare. The top bracket should be relatively easy to find (eBay, etc) as the nylon and spring steel ratchet assembly is usually trash by now (I saw several 3~4 yr old ones rotted out when I worked at Honda dealers) Automatic adjustment rarely works properly, I found it easier to adjust when dismantled (but PITA as you have to assemble to check clearance)
Larger model hydraulic part is too big so if you find one get seller to take a pic with rule across mounting holes.
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 16, 2017, 10:45:19
If I can't find the caliper joint, I'll probably fab something up.  Shouldn't be difficult. 

On another note, I got it purring like a kitten.  Cleaned the carb bowl and the pilot jet.  I also think getting it converted from 6V to 12V helps it run stronger. 
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 18, 2017, 11:05:39
Trimmed up the front fender and mounted it. Need to trim the back more to round it off...

Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 18, 2017, 23:07:13
Finally got my order from SuperBriteLEDs and replaced all of the bulbs. Also replaced the flasher with an adjustable LED compatible one. Turn signals work well. Even the 6v headlight seems to work well with the 12v conversion.

Got a superbike bar from Dennis Kirk that I need to drill out for wires. I'm going to mount it upside down to see if that works well. Won't be as aggressive as a clubman bar.
Title: Re: 1975 Honda CB125S
Post by: hillsy on May 19, 2017, 04:18:40
Just cut some slots in the bottom of the switch blocks and run the wires underneath the bars. Seriously, drilling the bars and feeding wires through them is a pain in the ass - especially when you want to change them again.....which you probably will.......
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 19, 2017, 08:07:52
Thanks for the tip! Wasn't looking forward to drilling especially if I switch again.
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 20, 2017, 00:49:01
Got the superbike bars mounted upsidedown. Looks pretty good. The wife isn't so keen. She says it looks like a crotch rocket now. Thanks to hillsy's tip, I notched the controls to avoid drilling. Need to notch the right side a little more though.

I need to get better pictures tomorrow.
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 20, 2017, 17:48:58
Got it cleaned up a little with some help from the youngest. Hopefully she'll appreciate this enough to want it someday.
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 20, 2017, 17:51:18
I also noticed that the steering stop is either broken or purposefully allows more turn to the right. The horn button will hit the tank when parked on the kick stand.
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 20, 2017, 20:33:29
Cleaned the chain and ran it on the center stand. Boy that back wheel needs some truing!
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 24, 2017, 13:51:09
Picked up a used set of forks with the springs on the inside to clean up the front end.  My gators and dust seals on the stock forks are falling apart.  Also waiting on a replacement front brake switch and throttle cable. 
Title: Re: 1975 Honda CB125S
Post by: Sonreir™ on May 24, 2017, 13:54:27
Verify your voltage levels with a decent multimeter. I ran a WPS for a while, but they're cheap and not very fault tolerant. That type of voltage regulator isn't always up to the requirements that LI-ION demands. So long as you're topping out at 14.5V or less, you should be OK. Give it some revs and if the voltage holds steady, you should see a good life out of it.
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 24, 2017, 13:58:35
Thanks!  I'll check it tonight. 
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 24, 2017, 17:21:55
Thanks for getting me to check the battery. Should have checked earlier the stator output. Seems to be flat. No voltage. Nothing on pink or yellow. Battery was at about 8v. Picking up a charger. Need to check stator. And the wires in between.

Would a 360 stator fit?
Title: Re: 1975 Honda CB125S
Post by: Sonreir™ on May 24, 2017, 17:25:40
Unfortunately, 8v is probably dead for LI-ION. They don't usually charge back up from being that low.

360 stator should fit, but I think the timing marks might be different?
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 24, 2017, 17:27:09
Damn. I'll double check disconnected voltage.
Title: Re: 1975 Honda CB125S
Post by: kwak250 on May 24, 2017, 19:30:10
Got the superbike bars mounted upsidedown. Looks pretty good. The wife isn't so keen. She says it looks like a crotch rocket now. Thanks to hillsy's tip, I notched the controls to avoid drilling. Need to notch the right side a little more though.

I need to get better pictures tomorrow.

I like the barsdid you have to replace cables etc with it being lower?


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Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 24, 2017, 19:35:53
Thanks. I should shorten the cables, but rerouted them for now.
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 24, 2017, 21:01:17
Pulled the battery and replaced it with a large cap in hopes that I could still get it to run, but no love. Only with the battery...
Title: Re: 1975 Honda CB125S
Post by: kwak250 on May 24, 2017, 21:16:02
Pulled the battery and replaced it with a large cap in hopes that I could still get it to run, but no love. Only with the battery...

Try using an AGM battery, it's heavier but can also be place on its side too


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Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 24, 2017, 21:18:31
Yah, leaning that way. Just ordered a li ion charger thinking I'd keep the WPS, but returning to Amazon and will also return the charger and get an AGM battery.
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 24, 2017, 22:55:50
Ok, did some research tonight. Learned that these bikes won't start if the battery goes flat or is not installed due to the ignition type. Battery required to create spark.  Might just pick up a cheap lead acid battery for now to try to figure out if my charging system is working. My aftermarket regulator rectifier may not be working also.
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 24, 2017, 22:58:49
Started mocking up the seat. Didn't get pics as the dogs were being a-holes so I had to go in for the night.

The seat will only be about 6" wide and about 22" deep total. Seating area will end at about 16". That seems to be where I'm comfortable.
Title: Re: 1975 Honda CB125S
Post by: kwak250 on May 25, 2017, 01:24:05
Started mocking up the seat. Didn't get pics as the dogs were being a-holes so I had to go in for the night.

The seat will only be about 6" wide and about 22" deep total. Seating area will end at about 16". That seems to be where I'm comfortable.
I'm following


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Title: Re: 1975 Honda CB125S
Post by: flamelspy on May 25, 2017, 11:08:48
Very nice job! I'm currently building a Honda ML125 1983, turning it into something between a brat and a scrambler.
Liked what you did in your front fender, looks like what i wanna make with mine, besides it's a little rusty.
Following thread and keep on!
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 25, 2017, 15:57:29
Got to love these little scoots. Look forward to seeing that.
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 25, 2017, 16:01:02
Have the seat mocked up. Have to love heavy cardboard and a hot glue gun.  Trying to get some old cans of spray foam to cooperate and fill in the voids. If this looks satisfactory, I'll cut out some plywood to use as a buck and cover with fiberglass.
Title: Re: 1975 Honda CB125S
Post by: kwak250 on May 25, 2017, 21:43:55
Have the seat mocked up. Have to love heavy cardboard and a hot glue gun.  Trying to get some old cans of spray foam to cooperate and fill in the voids. If this looks satisfactory, I'll cut out some plywood to use as a buck and cover with fiberglass.
Green florist foam works great and you can shave it and sand it down nicely


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Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 25, 2017, 22:35:39
I always forget about that stuff. I have something similar to balsa foam that I might try. I'm not the best at keeping things symmetrical though. So carving might not be much fun. With these templates, I have things fairly symmetrical.
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 28, 2017, 16:31:57
Got the bar end mirrors today. So installed them. Also replaced the broken front brake light switch.
Title: Re: 1975 Honda CB125S
Post by: kwak250 on May 28, 2017, 23:12:08
Got the bar end mirrors today. So installed them. Also replaced the broken front brake light switch.
Nice yeah mine isn't perfectly symmetrical either but close enough for a first time, next one will be made when I take off the plastics and make fit closer to the frame, I'll also have to make a seat pan at the same time, it's hard though cause I use it as a daily runner too


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Title: Re: 1975 Honda CB125S
Post by: flamelspy on May 29, 2017, 15:59:39
Nice seat pan! I made mine with pure fiberglass directly molded on the bike. Think it doesn't need greater reinforcements, since the body weight is totally on the bike frame.
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 29, 2017, 16:26:19
I assume you put down a layer of plastic sheet to protect/allow for easy removal?
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on May 31, 2017, 20:54:02
Looks like I fried the coil.  It was the stock 6v one. Found an aftermarket one cheap on Amazon that looks like a direct replacement.

New AGM battery installed also.
Title: Re: 1975 Honda CB125S
Post by: flamelspy on Jun 01, 2017, 10:59:51
I assume you put down a layer of plastic sheet to protect/allow for easy removal?

When molding the fiberglass on the frame?
I put some newspaper hehehe.
and used it to isolate/protect the gas tank too, since i needed it on place to shape it perfectly.
Works like a charm, and it's free!
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on Jun 01, 2017, 12:07:51
That works!
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on Jun 08, 2017, 09:09:16
Kind of got the coil sorted.  It wasn't bad.  Not sure why I wasn't getting spark.  Got it running again for a few minutes while I tried to sort out the brake lights, but now it won't run for more than a few seconds.  And as soon as I give it gas, it pops and shuts off.  And the interval keeps getting shorter for run time the more I try to get it going right after it dies.  I'm wondering if it's points.  Also need to double check the regulator/rectifier. 
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on Jun 08, 2017, 11:29:43
I also just replaced the float needle.  I wonder if float height would affect this?  Need to double check that.
Title: Re: 1975 Honda CB125S
Post by: crazypj on Jun 09, 2017, 15:49:15
You should always check and re-set float level when you fir new shut off parts
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on Jun 12, 2017, 10:09:49
Float level FTW.  I was checking it wrong.  Got the level set correctly and it's now running.  Thanks!
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on Jun 20, 2017, 16:07:53
Ordered some Avon AM83's.  Current tires are old and not quite the right size (too wide up front). 

Need to figure a way to remove the rear fender and remount taillight and turn signals.  Might just trim the fender up.
Title: Re: 1975 Honda CB125S
Post by: crazypj on Jun 26, 2017, 12:37:52
You need a smaller tail light, the original Honda one is huge.
I like the 60's style Lucas but prefer the 'raw alloy' to chrome plated
http://www.ebay.com/itm/Lucas-Style-Motorcycle-12V-LED-Tail-Light-For-Triumph-British-Cafe-Racer-Chrome-/262759607036?epid=2102678645&hash=item3d2db16afc:g:k28AAOSw6DtYTrBt&vxp=mtr
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on Jun 26, 2017, 13:16:53
Definitely want a smaller taillight.  That one looks like it would work well.  I wonder how well that would fit the fender?
Title: Re: 1975 Honda CB125S
Post by: crazypj on Jun 26, 2017, 16:04:40
I've only fitted them to CB360's. Modified to fit over rear frame rail (like later 60's/early 70's Triumph's)
(http://i91.photobucket.com/albums/k315/1crazypj/Honda%20CB360/CB360LUCAStaillightmod.jpg)
 I really should have taken a few measurements plus made a template to cut on it but I wanted to see it in position I just used a carbide burr
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on Jun 27, 2017, 13:11:25
crazypj, Do you have a shot from the back?  Looks like it fits well.

Just replaced the throttle cable last night (took the slow boat from China to get here 2 months after ordering, but it's NOS Honda and was cheap).  Nice and smooth now.  Waiting on new tubes so I can throw the Avons on. 
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on Jun 28, 2017, 14:17:55
Latest... Keeping stock seat for a while.
Title: Re: 1975 Honda CB125S
Post by: vwrabbit on Jun 28, 2017, 23:12:46
Front Avon tire mounted. That was fun.

Also cleaned up the rim.