Hoses On Carbs

[angus chapman]

hi all

just wondering - i have 3 black hoses/tubes connected to the carbs on my 78 gs750e. The centre one (between 2 and 3 carb) is blocked off, while the outside ones are open. is this correct? what do they do? should the outside ones be blocked off like the centre one?

cheers
gus

[denydog]

I am going through this with my bike right now. On mine the center tube is fuel from the tank, tee'd into the #2, #3 Carbs. The two outside ones are vent tubes, and just lead towards the ground from what I've read in the old posts.

[Redman]

Possibly the 2 outside tubes are overflow-vents like said before, yes, leave open, usally run up and over and behind the air box and then down toward the ground.

Possibly the center tube that it blocked off, is the vacuum line. Is it attatcehd to the intake boot of carb #2? If so, then , yes it is the vaccumn line that is intended to operate the automatic petcock. But maybe you no longer have that.

In your accounting of the lines going to the carbs, you didnt mention one that would be the fuel feed , er, petrol supply.

[renobruce]

The tubes you are referring to are for ventilation and vacuum. The two outside tubes are vented to atmosphere. If you have pods on the bike, leave the tubes off. The center tube is vacuum to your petcock. If you don't have a vacuum petcock, the center one gets plugged.

[ericox]

make sure your route those vent tubes correctly or you will have loss of power at high speeds, trust me. Mine route down the inside of the side covers.

[angus chapman]

i do have k&n style pods on the bike - was is the reason for taking the tubes off then? a friend of mine told me that the tubes were for adjusting the carbs and they should be blocked. i put screws in the end and i don't know if its psychological or not but the bike seems to be smoother.

i forgot to mention that the bike is fitted with a kawasaki tank, so no vacuum petcock.

cheers
gus

[Tarbash 27]

well keep carb 3 blocked and the rest open.

[angus chapman]

thanks for all your help guys.

gus

[renobruce]

i do have k&n style pods on the bike - what is the reason for taking the tubes off then? a friend of mine told me that the tubes were for adjusting the carbs and they should be blocked. i put screws in the end and i don't know if its psychological or not but the bike seems to be smoother.

i forgot to mention that the bike is fitted with a kawasaki tank, so no vacuum petcock.

cheers
gus

According to the carb gurus here, if you have TRUE K&N filters on the bike, it will starve for fuel at high rpms unless you take the vent tubes off. Dyno Jet also tells you to remove the vent lines when you re-jet with their stuff. You may not have a problem if they are not K&N's, but you do need to unblock them. As stated, plug the center nipple if you don't have a stock petcock.