1979 v 1980 carb differences

[itsacbx]

Hey all, I have two sets of carbs, one is off a 1979 motor and the other is off a 1980....
How can I tell which belongs to which engine?
Im rebuilding the 79 motor now and the 1980 is in my running bike but most importantly I want to make sure I match the correct carbs to the original engine.
Thanks
Al

[CBX-tras]

The rack from a '79 will only have one fuel inlet and NO AFV.
The rack from the '80 will/should have the AFV and 2 fuel inlets.

[steve murdoch icoa #5322]

Some more info with number i.d.
viewtopic.php?t=7034

[daves79x]

VB 60 (or 61 for world market) carbs are '79. VB62 (or 63 for world market) are '80 carbs. It's stamped on every carb on the rack.

Dave

[itsacbx]

excellent, thanks for that...
Al

[itsacbx]

But does the 80 carbs only have the screw in main jet plus two pressed in jets and no rubber plug???
My 80 won’t start and I’ve stripped the carbs twice and can’t see nuthin’ wrong. All floats with the flat edge of the float parallel to the carb body /at 15mm
Carbs cleaned and blown out , chokes working fine ….
But she won’t start , without ‘start ya bastard ‘ chemical assistance….gggrrrrr…..
Al

[broook]

Try bypassing the inline diaphram but always remember to turn off the gas when you park it.

[daves79x]

Did you verify that fuel is actually reaching the bowls? As Bob says, do you still have the vacuum valve attached and is it verified to work? If you are getting fuel, then it's still the carbs. There could be lots of things still wrong. The most profound thing I've ever found when the owner claimed to have rebuilt the carbs, then brought the bike to me, was that he had installed all the floats upside down.

Have someone do the carbs that has proven experience.

Dave

[CBX-tras]

But does the 80 carbs only have the screw in main jet plus two pressed in jets and no rubber plug???
My 80 won’t start and I’ve stripped the carbs twice and can’t see nuthin’ wrong. All floats with the flat edge of the float parallel to the carb body /at 15mm
Carbs cleaned and blown out , chokes working fine ….
But she won’t start , without ‘start ya bastard ‘ chemical assistance….gggrrrrr…..
Al

1980 Carbs are a 2 circuit design. The main jet that feeds the slide needle and the pilot jet (or sometimes called) the idle jet, circuit that is pressed-in.
The idle jet MUST be extracted to properly clean and verify the jet AND the circuit it feeds. Crud will grow in there like a ship in a bottle that can't be removed otherwise. No rubber plug used. Plugs are only used on 3 circuit carbs like the '79 version CBX and other Honda's.

[itsacbx]

Ive done the following:
1. floats are in correctly and set at 15mm.....
2. Ive blown out the primary circuit as best as I could with a couple of cans of carb clean and 70 psi and gently stuck a small diameter piece of wire as far as possible without getting too carried away.
3. internals of the carbs generally are spotless.
4. #4 carb still has the yellow paint on the nearest adjuster.
5. Distance from the butterfly slide to the first tiny hole in the carb throat is identical on every carb.
6. Carbs are not leaking.
7. Plugs are new
8. Vacuum fuel valve is removed and a T is in the fuel line to feed both carb feeds off the one tap spigot.
9. Chokes are working perfectly.
10. Idle adjuster screw is three turns onto the plate if you know what I mean.

Just to eliminate an possibility of it being an electrical issue, I replaced the OKI set with another set and the bike sparks on all 6 as required.

With choke fully on and no throttle, the engine stumbles along and along and along.......
Al

[daves79x]

You have not removed and cleaned the #35 press-in idle jets. That is very likely your problem. These things are too hard to take off and on to just use a shotgun approach to carb rebuilding/cleaning. If you mean that the mixture screws are three turns out - that's way too much. Two turns max. But you should have removed them all, along with the springs, washers and o-rings to verify that circuit, as well as that all the correct parts are there (many times o-rings and washers are missing or more than one each are found there).

This doesn't have much to do with starting, but did you wet test the rack on the bench before installing them? Did you verify that the accelerator pump is working correctly?

Dave

[itsacbx]

Thanks for the reply - mixture screws are 1 and 1/2 turns out. Carbs were bench tested - no leaks.
The 3 turns I was referring to was the idle adjuster . It was my way of trying to describe how far I’d turned the idle adjuster after it contacted the plate which moves all the butterflies (not the pilot screws)
Accelerator pump is working fine and squirts fuel as needed. O ring is in place.
I do not have the ability to remove the fixed jets nor do I want to . I’ll persevere with trying to get those circuits clean.
Al

[daves79x]

That's not how you bench set the idle. You turn the adjusting screw until it contacts the tab on the bell crank. Then you watch the throttle plates open. You want just a tiny bit of the first hole in the carb throat exposed. You have it way too far open at three turns. Usually just a fraction of a turn after contact.

Dave

[itsacbx]

I think thats problem- there is a big gap between the bottom of the plate and the carb Venturi . While one of the adjuster screws still has the factory yellow sealing paint on it the others don’t so my guess is the idle has been fooled with. There is probably 1/32 between the first hole and the edge of the throttle valve or maybe a little more.
Al

[daves79x]

You need to do a complete bench sync. Yellow paint means nothing if you’ve separated the carbs. They all need set to match #4. I think you are not understanding how this is done. I can walk you through it, but not here.

Dave