Topic: carbs with an without atmospheric vent tubes....

[bchaley40]

Hello group, I have a 78'CB 750 K8 I have a couple if questions. First I have a set of carbs that the jet tube has been eroded on the number 4carb an the carbs have the atmospheric vent tube, I have another set of carbs with out the atmospheric tubes but the screw holes are stripped out of the number 2 carb. My question is what does that atmospheric vent tube do an can I plug it off an use the number 4 carb off the other set? Or do I have to keep them all the same

[hsas.69]

You will need a vent of some sort otherwise the fuel will not flow into the float bowls. Without more info/pictures of the specific carbs can't tell you much more than that.

[bchaley40]

Here it's the number 4 carb with the erosion

[bchaley40]

Carb that has no atmospheric vent

[bchaley40]

Carb set with the atmospheric vent

[harisuluv]

The ones without vents actually do have vents.  the hole is just smaller, instead of a nipple it has a small hole about 12 thousandths thick

[bchaley40]

Ok so cash I plug the number 3 carb off an still use the other number 4 with the smaller vent our will this not work?

[harisuluv]

each carb needs an atmospheric port.

[harisuluv]

are you asking if it's ok to just mix and match 77 and 78 carbs?  Well... I guess..  The internals are going to be different though.

[bchaley40]

It seems the only difference is the size of the atmospheric port an i was thinking running the 78 carbs just as they are an plug number 3 on the side it would of gone to number 4 running the 4th as it would on the 77 it. Seeems the internals are the same such as jet needles an such but if its to different then i will just look for a set of 78 carbs or a 78 number 4 an go that route in the first pick is the erosion to bad to continue using i can still thread in the tube an jet.....

[harisuluv]

i should have a few 74 number bodies.  all i need is casting number and #carb (4)

[bchaley40]

Not sure if this it's the right number but here you go

[flybox1]

Needles are different between 77 and 78 carbs.  77's have adjustable clips.  78's do not. 
I have a spare set of corroded carbs just like yours.  There are plenty of good, usable, components. 
I hope you dont toss them.
Harisuluv can provide you with many parts. There are also a few good, usable sets on feebay...

[bchaley40]

No I want planning on getting rid of them an I just ordered a set on eBay. An looking on the carbs they both look the same only difference was the atmospheric vent port one has the tube between all carbs the other just the small hole other than that all needles are the same