collapse

www.dimecitycycles.com

www.cognitomoto.com

https://www.townmoto.com/collections/vanson-leathers

www.speedmotoco.com

www.CITYLIMITMOTO.com

www.jadusmotorcycleparts.com

www.lostapostlejewelry.com

www.sparckmoto.com

www.pistonsociety.com


Author Topic: New to DTT, and starting a '73 CB125 cafe build!  (Read 21805 times)

Offline nrcb125

  • Posts: 280
New to DTT, and starting a '73 CB125 cafe build!
« on: Nov 07, 2012, 20:20:44 »
Hey everyone as the title suggests, I'm new to DTT and I picked up a CB125 today. The idea is to build a very basic cafe racer. As of now the plan is to clean everything really well, then make a fiberglass tail-section and put some of the finest Chinese clip-on handlebars on it. I may CNC some rearsets for it as well once I get a chance to sneak into my university's machine shop.

Are there any CB125 quirks I should look out for?

And here's a photo!
'73 CB125S - current project
'99 EX500 - Race Bike


CB125S build thread (haven't updated in 5ever): http://www.dotheton.com/forum/index.php?topic=43403

Offline joeyputt

  • Posts: 1326
  • The green flag sets me free
    • dwmsracing
Re: New to DTT, and starting a '73 CB125 cafe build!
« Reply #1 on: Nov 07, 2012, 22:10:53 »
Welcome to Dotheton Brother! Congratulations on your new bike, she looks like she is in really good condition!
Joe - Owner/Operator of DWMS Racing World Class Engine & Motorcycle Building www.dwmsracing.com

Cylinder Head Porting Sale! http://www.dotheton.com/forum/index.php?topic=56203.msg637024#new

Facebook https://www.facebook.com/joe.dwmsracing

Offline VonYinzer

  • DTT SUPPORTER
  • *
  • Posts: 18379
Re: New to DTT, and starting a '73 CB125 cafe build!
« Reply #2 on: Nov 07, 2012, 22:29:07 »
The 125 is as simple as a four stroke can be. Great first project.

If I can suggest something though... Forget buying some shitty chinese crap parts. If you can cnc rearsets, you can make your own clip ons. Make your own parts any time you can, and if you can't keep your money local. Clip ons and many other "cafe" parts that you can buy from Asia can be whipped up from better materials by locals (or yourself) for the same or in many cases, less money.

Ok, off my soapbox now. Keep us posted on the build!
Like a river that don't know where it's flowin'
I took a wrong turn and just kept goin'

Offline Rat_ranger

  • DTT BOTM WINNER
  • *
  • Posts: 363
Re: New to DTT, and starting a '73 CB125 cafe build!
« Reply #3 on: Nov 08, 2012, 01:07:51 »
The dent in the tank is in a great spot to base knee dents off of.  You can find about anything you want for that motor, but for a starting point that is a nice clean bike.

Offline nrcb125

  • Posts: 280
Re: New to DTT, and starting a '73 CB125 cafe build!
« Reply #4 on: Nov 08, 2012, 12:49:05 »
Day 1 Update:
My afternoon class was canceled and I got out of lab 2 hours early so, time to get working! The bike wasn't running when I picked it up, but did have good compression. The PO said the battery was dead. It sat in a charger while I went to work cleaning the carb and tank. The good news: there was no rust in either. The bad news: the copper fuel filter inside the petcock had started corroding leaving nasty green residue everywhere. Cleaned everything up and put everything back on. Got her started and she purrs like a kitten.

The throttle cable seems to be stuck and I'm not sure what to do about it. Going to try cleaning/lubing the cable. Any other ideas?



Day 1.5 Update:
I got the throttle working. Some cable lube had to be applied to the slide in the carb to get it unstuck. I had a bit of trouble with the petcock reassembly and there's now a gallon of gas in the driveway... But, she runs! And pretty well. The last thing to do is adjust the jetting so she'll idle without the choke fully engaged.
« Last Edit: Nov 08, 2012, 17:19:29 by nrcb125 »
'73 CB125S - current project
'99 EX500 - Race Bike


CB125S build thread (haven't updated in 5ever): http://www.dotheton.com/forum/index.php?topic=43403

Offline nrcb125

  • Posts: 280
Re: New to DTT, and starting a '73 CB125 cafe build!
« Reply #5 on: Nov 28, 2012, 21:38:07 »
So far I have:
  • Replaced the oil
  • Troubleshot the electrical system (grounded where it shouldn't have been)
  • Troubleshot the carb and found the float had holes in it. The entire carburetor was replaced the carburetor with a cheap Chinese one as it was only $5 more than a replacement float
  • Realized the front brake is absolute garbage

After looking into fixing the front mechanical brake or replacing the front wheel with disc for one with a drum brake, I decided to ditch all of it in favor of a hydraulic setup. By chance I had a complete '95 Ninja 250 front brake setup. A simple bracket should make everything fit nicely.

I'll keep this thread updated with everything I do.
'73 CB125S - current project
'99 EX500 - Race Bike


CB125S build thread (haven't updated in 5ever): http://www.dotheton.com/forum/index.php?topic=43403

Offline nrcb125

  • Posts: 280
Re: New to DTT, and starting a '73 CB125 cafe build!
« Reply #6 on: Dec 01, 2012, 20:33:17 »
Another update:
I've measured and modeled what would need to be made to fit the Ninja 250 front brake caliper to the CB125S and plan on having the on campus machine shop make it in their CNC machine for cheap. Attached is a rough model of it in Google Sketchup.
'73 CB125S - current project
'99 EX500 - Race Bike


CB125S build thread (haven't updated in 5ever): http://www.dotheton.com/forum/index.php?topic=43403

Offline nrcb125

  • Posts: 280
Re: New to DTT, and starting a '73 CB125 cafe build!
« Reply #7 on: Dec 07, 2012, 17:53:42 »
I decided to nut up and buy some XR100 forks for my CB125. They should be here sometime next week. The good: same tube diameter as the CB125, same axle diameter, and a hell of a lot more spring options. The bad: the fender mounting holes may not line up, the forks are definitely going to be longer, and I'll need to redesign the front caliper bracket. It's going to be interesting to see if the XR100 forks work.
'73 CB125S - current project
'99 EX500 - Race Bike


CB125S build thread (haven't updated in 5ever): http://www.dotheton.com/forum/index.php?topic=43403

Offline mbott

  • Posts: 5
Re: New to DTT, and starting a '73 CB125 cafe build!
« Reply #8 on: Dec 12, 2012, 21:18:03 »
Awesome! I'm pumped for you and your build!

I recently started a 125s build but it's pretty bare-bones.  I got it running but with no seat, electronics, speedo or tac. The thing was a tracker so it was essentially a blank canvas.

I have never done mechanical work before and I have no reference for what a cb125s should look like. Can you please send me some pics of the wiring and electrical system on your bike? Also, in my photo, what is the thing circled and highlighted in red? What is it attached to on your controls and what is it's function?

Offline nrcb125

  • Posts: 280
Re: New to DTT, and starting a '73 CB125 cafe build!
« Reply #9 on: Dec 15, 2012, 16:15:17 »
I think, and someone please correct me if I'm wrong, it's the tachometer cable. On these bikes they're driven exactly like a mechanical speedometer. As far as wiring, my bike is pretty much bare bones as well. There's a huge rat's nest of wires in the headlight bucket. Pictures won't help you there. I found a link to the cb125s service manual here on dtt. It'll be at the bottom of this post. Hope this helps you!

As an update, the XR100 forks fit! But the top of the triple tree is completely different so there's no way to mount them... I spent a few minutes on ebay and found an XR100 triple tree, steering stem, bearings, etc for only $25. I also snagged some .41kg/mm from BBR for the XR100 forks. Everything should be here next week!

Link to CB125S manual:
http://www.dotheton.com/forum/index.php?topic=20352.0
« Last Edit: Dec 16, 2012, 11:05:10 by nrcb125 »
'73 CB125S - current project
'99 EX500 - Race Bike


CB125S build thread (haven't updated in 5ever): http://www.dotheton.com/forum/index.php?topic=43403