CB125s My First 2-Wheeler - stretched and mono-shock

Re: CB125s My First 2-Wheeler

I'm liking this................
 
Re: CB125s My First 2-Wheeler

been a while since Iv done any work on this bike!

got the itch to get it back out on the road this summer which led me to making a new simpler exhaust with a better muffler and also trying out a mono-shock setup..

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It seems to be a bit on the soft side, it think if I get a stiffer shock, or one with some preload adjustment it could work OK

The monoshock mounts are temporary to find a good position and angle, i'll beef them up if it all works out.

https://www.youtube.com/watch?v=Z-m6jF-Nfq0
 
Nice there was an update!

This is my fav CB125s build in the entire world and you had helped me out once before because I am trying to build my CB125s to be like yours :p

I imagine you changed the exhaust due to clearance issues with the rear tire? (hope not, was hoping to have the same stance lmao) I love the look of the small box exhaust by the feet it's very cool although I wonder if it would run a little hot :p Do you mind letting us know what exhaust muffler you're using?

With my version of the build I won't be trying to go mono-shock with it but am soon going to be bringing my bike to a welder for a new exhaust and to try and stretch the swingarm similarly to yours.

Sick build man I really think you're making the best out of an 80s CB125s.
 
Thanks Royal, I changed the exhaust to give myself more room for the monoshock setup and also I always smell like exhaust when I get done riding this bike, I am hoping to reduce that with the lower positioning. Otherwise the exhaust cleared the rear tire just fine with the dual rear shock setup. Rode the bike for two summers in the previous configuration with no problem, other than the lack of adequate brakes.

The muffler is from the 'Motoped' bike, their website always lists this muffler as sold out but I found someone distributing them on Ebay.

I went ahead an fab'd up the permanent swing arm. I ditched the extensions and lengthened the arm the same amount with tubing. I added some preload and raised the mounting point for the shock and that seemed to really firm up the travel. I still need to make a hoop from the shock to the rear axle but I need to get more steel.

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Finished up the swingarm

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the back is nice and firm, now I need to work on the front suspension

https://www.youtube.com/watch?v=OAHTb5vPK2k
 
That looks pretty fuckin' sick man awesome work! thx for info on the muffler.

In case I want to go monoshock and to just put the info out there for anyone who comes across this in the future : how much length did you add to the original swingarm when you stretched it? and what type of shock did you use for the monoshock? In your second video it seems to be alright with your weight and doesn't dip too low. Stiffer springs in your front suspension and heavier fork oil and you should be good to go!

I'm at the cusp of finishing the 12v conversion for my CB125s and after that I'm off to the local welder to make some rearsets and extend my swingarm as well. Right now I'm not thinking monoshock but if I show him your work and he says he can recreate it I might copy ya :p

Lastly, you likely got a longer chain due to the extension of the swingarm...but how is it liking the new stance with the monoshock? clears the frame and everything no chance of rubbing?
 
added about 3.25" to the arm. The shock is the OEM part from a Honda Grom, and I added about .25" of preload.

The chain clears the upper loop of the swingarm by a finger so its good, it can slightly brush the swingarm pivot, just as it always has.
 
Awesome info man thanks for sharing ! Yeah the chain barely clears even on stock setup on this bike but no matter you made it work.

Did you end up going 12v with yours? I just connected the Sparck moto rectifier/regulator last night to my wiring and put in 12v bulbs and my new headlight and tested it.

Turning signals were working and so did the brake light but headlight didn't turn on so I figured the bike needed to be running. Went to go to the gas station to refill a jerry can and by the time I had filled the tank and set it back on the frame the lights didn't work anymore and I had blown the new 15A fuse I put in to replace the 10A fuse.

Was confused as to what went wrong but then I had an epiphany and realized I had mistakenly connected the regulator near the coil when that was uncessary due to the new recti/regu combo piece. I'm hoping that was the case and when I try it again it doesn't blow the fuse....

Keep us posted! great stuff ;P

Edit June 2nd 2017 : To those reading this post. It turns out I was wrong about having both the original regulator on and my new rectifier/regulator at the same time. I mistook the "CDI Unit" on this bike to be a regulator, and the actual voltage recti/regu to be just the rectifier. Both units look identical and that is what caused the mistake. The cause of my blown fuses might be caused by my improper anchoring of the rear-frame ground. I am currently investigating this and will report back when I repair the eyelet connector for the rear frame ground.
 
I went partial 12v you could say.

I ditched the battery on my bike so the electronics only work when its running, and I have the lines to the ignition left in the original configuration.

The headlight is a piaa auxiliary driving light meant for a car that works just fine off of the original unregulated AC headlight feed since its incandescent.

The only other light I have is the brake light. I used the stock rectifier/regulator feed (6v) that would usually power the brake, gauges, indicators, and charge the battery and fed that in to a DC to DC step up converter to get 12VDC. I use the 12V to power my LED driver and power the microcontroller that activates and strobes my brake light. I only need about .7 Amps to power the LEDs and .05 Amps for the micro so the step up converter works very reliably and iv never had a problem with it.

where did you splice in the rect/reg at? should be using the lines that fed the stock one that you said you left connected
 
Wow that is a very interesting solution for your electrical. I know not many people will use your set up due to the lack of indicators yet that is still very good info to put out. It's hard to find info re: 12v conversions for the CDI '81-82 CB125s bikes. If I am unable to get this 12v conversion to work maybe I'll consider what you have done and figure something out for the indicators.

I was wrong above about keeping the original regulator on while using my new one. Turns out I mistook the "CDI unit" as the regulator because it looks identical to the voltage rectifier/regulator which I mistook as a simple rectifier only. It sounds hilariously stupid but I think the reason my fuse is blowing is because my rear-frame ground is not properly installed...I feel dumb but I had it taped to the frame with electrical tape since the eyelet connector is broken. I'm replacing that this weekend and will have it securely fastened. My guess is when I went to switch off the power with the key the frame ground was ineffective at dumping the electricity into the frame and thus it blew the fuse.

To answer your question regarding the new regulator/rectifier I have. I used one of these from Sparck Moto who helped me out on this forum, great people : http://www.sparckmoto.com/Products --- Product is called : 12V Single Phase Regulator/Rectifier.

The white connector on that piece fit the connector on the original wiring but the corresponding ports were mismatched. I couldn't remove the brass connectors from the white case for the new unit so I cut them off and used Honda OEM original 3.9 mm female and male bullet connectors which I had to purchase from a guy in New Jersey : http://cycleterminal.com/ If you need to buy some discuss shipping options with the owner before placing an order...I think he uses USPS first-international but the service sucked ass. I'm only 8 hours away from New Jersey and placed an order on May 6 and it took 4 weeks to arrive..too slow.

So now all the right wires are connected to the right ones. Fingers crossed that my issue is as dumb as a bad frame ground. So excited to be able to ride the bike to the welder shop to discuss the future of the project.
 
Loose ground is probably not it. Quite the opposite, if there is no path to ground, no current will flow, you need 15A of current to blow that fuse that's quite a bit. Likely a short downstream of the fuse or voltage going too high.
 
It was a strange issue for sure Fifty and I had doubts about the ground myself but I just fixed it this weekend by putting a new eyelet connector on the ground, shaved off some of the powdercoating on where it bolts into the frame, and re-connected it and voila...now my 12v system works .

Tested it yesterday afternoon and now all my blinkers work at full brightness, headlight turns on when bike is on and so does the highbeam. Fuse didn't blow when I turned the key to off and I turned it back on three times to see if it was still working and yeah I'm looking good :p

All it took for my 12v conversion was new 12v bulbs, that Sparck Moto rectifier/regulator modded to work with original wiring, and 12v gel battery slightly smaller than the original 6v.

The only thing that sucks is the original headlight had a lot of space for the wiring to be placed into and my new headlight has no space. I have to work on a solution for tidying up the wiring.

Keep up the posts want to see more about how you're getting the new suspension to work for you !
 
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