Tee pieces between carbies - missing tubes?

[Anonymous]

I've been servicing the petcock and the tank is off so I can see into the carby area.

There is an "empty" tee piece between carbs 1 & 2, and another between 3 & 4. I suspect the things are the fuel line between the carbies. It seems that there should be a tube attached to these things, but there is a blank tee poking upwards with no tube. I don't have good light in the shed at the times I have to work on the bike, so can't see if they are blanked off or open to the air.

My service manual shows tubes in the tees, but doesn't show where they go. They do not appear to be linking the two tee pieces. There is no explanation of them in the manual's text.

Anyone know what the proper set-up should be?

Thanks
Kim

[Jay B]

Tubes.

Don't have my book in front of me or the bike but arn't those the vent tubes?

[moto_dan]

Yes, they are in the vent tubes.

[TheNose]

I've just rebuilt the carbs on my new '77GS750. It has a rubber hose about 1/2 inch long that connects to the sides of carbs 1 &2, and another that connects between the sides of 3 & 4. These are the gas lines between the carbs. There is a Tee between carbs 2 & 3 that goes to the pitcock connector on the outer side of the bike. Each carb has a nipple coming off of it on top that is a vent line, and each carb has a nipple coming off of it on bottom that is vent line, except for the one coming off of the bottom of carb three. It provides the vacuum to the pitcock connector that is toward the inside of the bike. You can put your finger over it when the bike is running and feel the vacuum.

The vent lines from the top should run up then back under so that the lines are mostly above the height of the carbs. They will turn downward, but most of the line will be avove the carb. The vent lines on bottom wil run down, probably on the right side of the bike.

[Anonymous]

The vent lines from the top should run up then back under so that the lines are mostly above the height of the carbs. They will turn downward, but most of the line will be avove the carb. The vent lines on bottom wil run down, probably on the right side of the bike.

I should have said first up that this is on a GS1000G. There seem to be two types of carby on the GSs - this has the Mikuni BS34SS carbs, the ones with the broad flat diaphragm head. Other bikes have the non-diaphragm type, the VM26SS which are thinner all over, and might have the upper vents referred to here.

These carbs have no vent at the top. The only thing that might be a vent are these nipples joining each outside pair of carbs at the level of the float valve. If it is a vent, what is it venting? The float chamber? The fuel line?

Am I likely to be losing fuel through it if there is no pipe attached to the nipple?

Kim
Taking the morning off work so I can see what it looks like in better light.

[Anonymous]

Maybe an obvious suggestion but I'll give it anyway. My GS1100G also has the BS34SS carbs and while taking them apart I found the set of carb removing & cleaning images on this web site to be pretty accurate and helpful. Maybe going thru some of these pictures can answer your problem.

Digno
1982 GS1100G

[focus frenzy]

I also have a 1000g and can say for sure that those are the carb. bowl vent/over flow lines, they should point down and have a rubber line connected to each one and the line runs down the back of the transmission through a hole in the casting, ending flush or a little bit lower than the bottom of the engine.

set up correctly, if a float sticks open, fuel should run out the vent line instead of filling the intake and cylender.

[Anonymous]

Thanks for your help, guys.

I checked the bike out this morning when I could see better and found that the nipples are not level with the float valve but level with the half-way point of the intake venturi. When I fitted a tube to one and blew gently down it the fuel came up through the main jet.

I've just looked over the carb rebuild photos and the vent nipple (and the tube) is clearly seen on those pics.

Seems I have to get some more fuel tube to replace the missing bits.

Thanks again
Kim