Topic: Carburetor Breather Tubes question

[Colonel]

Experts,

Still working on my carb.
I gave it a test blowing air in the breather tubes to verify everything was clear.
I have air coming out of the first two 'pressure equalizing' hole in carb 2 and 3 but only one in carb 1 and 4...
Moreover - but this is normal physics - Air pressure decrease through the circuit...
Problem or Feature? Should I get air from the second hole on carb 1 & 4?

[Spanner 1]

With the carbs 'dry' the air applied to the breathers can come out all over the place..!, wouldn't worry about it ...carbs look v.nice btw..

[Colonel]

Thanks for the feedback.I hope this is normal too.
The carbs do look nice for a 35 year old lady... but I have been tracking down problems with my CB750 K5 that led to my first carb job and I do discover and learn things everyday...
I thought I was ready to reassemble when I decided to check the air flow through it... I discovered a clogged fuel intake in one carb... Rust powder... 

[Colonel]

OK... I got it...
The pressure is equalized in carbs by pair as described  below (see updated illustration)

If you look at carb 1 & 2,  the breather tube connected to carb 2 is the intake; second hole in carb 2 is the outlet to carb 1 (through the small connection tube).
Same for 3 & 4. So carbs 2 & 3 (the ones with breather tubes) have two open holes/circuit, the other two just one (the second one is plugged).

Mainly trying to record this as it might be handy to someone trying to figure out how carb works...

[kghost]

correct.

its not really a breather.....

It allows atmospheric pressure to reach all the bowls.

More a vent system

[Mark L]

Hi,

Maybe you would be able to give me some advice on a similar query. Have recently bought a K8 which was only running on the two left hand cylinders. Points shot, blackened downpipes  so had been running rich, carb float levels way too high, no air filter fitted...
Carbs have come off for a clean. On the carbs there are two nozzles (see pic) The fuel line was plugged in to the one circled red, but what is the second nozzle (circled green) for? Is it for pressure equalization? What should it be connected to (if anything)?

Enlightenment would be appreciated.

Many thanks,

Mark
(UK)

[kvallelunga]

Mark,
The smaller of the two, higher in elevation is a vent, it runs up over your airbox down with the drain lines under the bike. The larger is the fuel inlet, attach it to your tank.

Kevin,

[Mark L]

Many thanks Kevin,

Regards,

Mark

[Colonel]

Mark,
The smaller of the two, higher in elevation is a vent, it runs up over your airbox down with the drain lines under the bike. The larger is the fuel inlet, attach it to your tank.

Kevin,

ABSOLUTELY...

[kvallelunga]

Glad I could contribute to this wonderful resource.