Honda CB125 Twin

[Nemo]

I need to adjust the idle screw, as it's a little high. Being a twin cylinder, it has two carbs, what I want to know is are they connected somehow? So there's only one screw, or a screw on each carb.....

The original handbook doesn't really help much.
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Previously owned: Kawasaki KH125, Suzuki GP125, Suzuki GX 125, Honda CB125 TDC '83, Honda ntv 600, Kawasaki ER5, Kawasaki ZZR600, Aprilia RSV 1000 Mille
Now own: Ducati 848 evo

[CarlosCBR]

I imagine there would be one on each carb. Only connected by throttle cable iirc i dont think they share the idle/misture screws too.
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[Frost]

Turn the throttle back and forth and look at the carbs. You'll see bits of metal moving back and forth. where they come to rest is where you will find the idle screw. Yes both are connected.

[Nemo]

[Blau Zedong]

[Vincent]

I think the tickover is only set on one carb, usualy the L/H one. Our resident CB125T expert will be along shortly, just make sure you're sitting comfertably

[Frost]

Number 11

[Blau Zedong]

[Vincent]

[fiery tupp]

Is it this type ? though it's for a cb 125 t
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If you can't fix it with a hammer , use your head .

[Vincent]

[Teflon-Mike]

[Nemo]

Thanks for the advice, Tef, think you'll be the best to ask, I want to start this all over again.

So once the carbs are balanced, can I turn the idle screws in all the way, then bring them both out at the same number of turns? Or is this just stupidity?

Do you know what they say the setting should be? Like 2 turns...3 turns?

Just wondering if that would be easier, the pilot screws I want to keep away from really, as the mixture seems fine, or should I do the same with these, turn them both all the way in, then same number of turns out....
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Previously owned: Kawasaki KH125, Suzuki GP125, Suzuki GX 125, Honda CB125 TDC '83, Honda ntv 600, Kawasaki ER5, Kawasaki ZZR600, Aprilia RSV 1000 Mille
Now own: Ducati 848 evo

[Pete.]

I hate split-cable twin carbs. My GT250 had them.

I don't know what the factory say is the proper method of setting the carbs but here is how I would do it, supposing I wasn't going to pull the carbs off the bike and measure the slide lift beforehand.

Open the throttle slightly and screw in both idle screws a bit so the revs increase to fast idle.

Slacken the cables now to increase free-play.

Using vacuum gauges, balance the carbs by winding out the idle screw on the high reading carb until the vacuum is the same then keep adjusting each down in turn keeping them balanced until the idle is set.

Now set the free play on each of the split cables (might only have adjustment on one in which case adjust that on so free-play is equal on both. Do this visually/by feel.

Set the free play on the main throttle cable

Now, with the vacuum gauges still attached, open the throttle very slightly and watch the gauges. If one lifts before the other, adjust-out the discrepancy.

Re-set the free play on the main throttle cable. Check lock to lock for revs rising.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[Pete.]

Needless to say, before you have done all this you will have checked that the float heights are the same on both carbs and the jetting is clear
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[P.]

[Nemo]

I found a set on e-bay for £20, but might see if I can get to machine mart, see ifthey have any, or maybe halfords.
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Previously owned: Kawasaki KH125, Suzuki GP125, Suzuki GX 125, Honda CB125 TDC '83, Honda ntv 600, Kawasaki ER5, Kawasaki ZZR600, Aprilia RSV 1000 Mille
Now own: Ducati 848 evo

[Vincent]

Can you use vacuum gauges on those carbs

[P.]

[Teflon-Mike]

[Pete.]

[Teflon-Mike]

[Nemo]

I want to try get the carbs done today, because it doesn't feel right, not aweful, but not as well as it could be.
Teff, would you be able to post on here, or inbox me a little step by step guide on how to balance the carbs as close as possible without using vacuum gauges? I want to do it before the week commute to work.
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Previously owned: Kawasaki KH125, Suzuki GP125, Suzuki GX 125, Honda CB125 TDC '83, Honda ntv 600, Kawasaki ER5, Kawasaki ZZR600, Aprilia RSV 1000 Mille
Now own: Ducati 848 evo

[Teflon-Mike]

Its in message above, basically.
But futile unless you have the choke butterfly's properly adjusted first.
If they aren't both fully open, then mixture goes ritch, and the idle will be all over the place.
1 lift seat.
2. disconect & remove battery.
3. remove air-boxes, so you can see the carb-bodies and butterfly's.
4. fiddle with linkage to get full travel on both chokes and balenced.
Use elastic band / spring / hair elastic trick to add holding pressure to link if needs be.
5. Bike on centre stand, use jump-leads to start bike without battery.
6. Open throttle a little, set high idle on idle screws.
7. Allow to warm up.
8. When warm & even idle achieved, wind out the idle screw on LH carb letting idle drop slightly, then lower RH idle to get even idle.
9. look down carb-mouths to see how level the slides are in the bodies, try and get them roughly level, as you go down.
10, having got the lowest even idle you can with the slides together, positively twist the twist grip as closed as you can, and hold it there, to get all tension off the cable.
You may have to back off the adjuster at the twist grip.
11. take up the slack on the cables at the carb-tops, one at a time watching to see when the slides start to lift, then back off a nadge, take up the tension, then lock, then repeat on other carb-top.
12. take up any remaining slack on the cable at the twist grip, then check both slides lift together. Repeat adjustments if necessary.
Once happy, check everything over, pop air-boxed back on, refit filters and battery....
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