CB125s carb question

hellhound1

hellhound1

Do No Harm. Do Know Harm.
I picked up a 1979 CB125S about a year ago before I knew of this site, I had to a complete top-end rebuild and the normal "build" we all go through. Now I'm on the home stretch and I've got it running and everything, bought a really cheap carb for now, but I was wondering if this:
http://cgi.ebay.com/ebaymotors/Mikuni-Carburetor-Honda-CB125-CB125S-CG125-CB-125-Carb-/370502130146?pt=Motorcycles_Parts_Accessories&hash=item5643a5d9e2

would work on my '79, and possibly run a lot smoother. The one I have now is a pain to adjust and flat out doesn't work well.
 
hellhound1 said:
I picked up a 1979 CB125S about a year ago before I knew of this site, I had to a complete top-end rebuild and the normal "build" we all go through. Now I'm on the home stretch and I've got it running and everything, bought a really cheap carb for now, but I was wondering if this:
http://cgi.ebay.com/ebaymotors/Mikuni-Carburetor-Honda-CB125-CB125S-CG125-CB-125-Carb-/370502130146?pt=Motorcycles_Parts_Accessories&hash=item5643a5d9e2

would work on my '79, and possibly run a lot smoother. The one I have now is a pain to adjust and flat out doesn't work well.
Click to expand...

I would be skeptical. Only because the model on eBay there shows that it fits the 1980-85 models while your bike was manufactured in 1978. Also, I'm not 100% on this but I believe the newer modeled 125s's had a larger carburetor and larger engine displacement which gave it 124cc's instead of 122.

I also have a 125s albeit a 1975 model and luckily have not had to toggle with the carb. You say you bought it cheap....how cheap??
 
No, will not work with your CB125

What makes your carb hard to adjust and not work well?

Is it the style of carb? the original Kehin? If so, heres all the info you need to make it run like a top
I think the carb is a PD66B
The main is #110
Clip in the third groove on the needle
Pilot screw 1 turn out
Float height 18.5mm
 
Hey thanks for the answers. Turns out the floats on this current carb would get stuck on the bowl resulting in either way too much gas or none at all. Also timing was a major factor, this little bike is extremely fickle about being exact, granted it should have been exact in the first place.
 
I just picked up a 1978 CB125S and the original carb is froze up. The throttle cylinder that slides up and down is completely frozen to the carb itself. I've tried soaking it over night, prying it up with a screwdriver and tapping it from the top with a punch - to no avail.

So no big deal because I just thought I would buy a new one, but I can't seem to find one anywhere! Does anyone know where I could buy a new OEM or performance carb that would work for this year and model?
 
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=140616913079

This is the critter you want for a little bit more zap.
 
4Nines said:
I just picked up a 1978 CB125S and the original carb is froze up. The throttle cylinder that slides up and down is completely frozen to the carb itself. I've tried soaking it over night, prying it up with a screwdriver and tapping it from the top with a punch - to no avail.

So no big deal because I just thought I would buy a new one, but I can't seem to find one anywhere! Does anyone know where I could buy a new OEM or performance carb that would work for this year and model?
Click to expand...

Find an ultra sonic cleaner and give it a bath it should free up.
 
Erskine said:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=140616913079

This is the critter you want for a little bit more zap.
Click to expand...

Thanks for the info!

I did some more research and figured out that 76' to 79' models didn't use the standard intake flange off of the carb. So that's why no one can find an OEM carb for these bikes. You have to retro fit an 80's or newer intake flange onto the motor and then bolt up a new carb.

Now the problem is I can't find a place to order the 80's + flange :/ Anyone know of a good place to order OEM Honda parts?
 
Barkingmadspeedshop said:
Find an ultra sonic cleaner and give it a bath it should free up.
Click to expand...

I'll give it a go! Is that something I can get at Auto Zone or O'Riley's?

I guess I'll just have to cut my throttle cable if I can't get it to free up :(
 
4Nines said:
I'll give it a go! Is that something I can get at Auto Zone or O'Riley's?

I guess I'll just have to cut my throttle cable if I can't get it to free up :(
Click to expand...

Call around and find someone that has one. Try a gun shop.
 
clean all of the solvents off it that you have sprayed on.

Next, take a small butane or propane torch

with the carb and cable off the bike, put the carb body in a vice so both of the 'mouths' are in each jaw, tighten down with enough pressure to hold it, but not break it

heat the sides of the carb body that the slide sits in, dont go crazy and turn it cherry red (it wont go that far, it will start melting) liberally heat all around the slide body.

Grab and ice cube and touch it to the top of the slide for 5-10 seconds, then give the cable a 'jerk' upwards

the heating of the body should expand the metal around the slide a bit to help free it up, and the ice cube is a cold shocker to help 'shrink' the slide itself

If that doesnt work, find a motorcycle shop with and ultrasonic cleaner and let them dunk it for a few hours
 
Erskine said:
Evilbay is your friend. And down fall ;)
Click to expand...

Yeah I've been keeping an eye on it everyday with no luck :/

Let me know if anyone knows of a good Honda parts store I could order from!
 
Researched and researched and I think I've found a fix for all the 76' to 79' guys - I think the intake manifold from an 85' CB125S will fit and allow me to run whatever aftermarket or OEM carb I want. The other good thing is my local Honda dealer was able to source the part and order it up. I'll keep you guys posted.
 
digging up the dead. did this solve your problems?
i've been interested in doing the same to mine. thanks.
 
1975blaze said:
digging up the dead. did this solve your problems?
i've been interested in doing the same to mine. thanks.
Click to expand...

It did! I used the 85' intake manifold, picked up a new Mikuni Carb and it runs like a champ :)
 
4Nines said:
It did! I used the 85' intake manifold, picked up a new Mikuni Carb and it runs like a champ :)
Click to expand...

Result! Could you tell me which Model Mikuni you used please?
 
Erskine said:
Result! Could you tell me which Model Mikuni you used please?
Click to expand...

I picked up this bad boy: http://www.tboltusa.com/store/mikuni-22mm-carb-p-375.html?osCsid=2e62447eeb0b410a3579ded3bb470e74

I live at about 600 ft elevation so I wasn't too worried about tuning. I slapped it on and it fired right up and has run well since. I haven't even spent one minute tuning it at all. I'm sure I could fine tune things a bit, but right now I'm just having fun riding it :)
 
Thanks for that link, it's good to know what will work.
Anyone know if there are any flat side carbs that will perform on this engine?
 
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