Carburetor : missing gas admission on middle carb

Hi all,

I’m in the process of dismanteling the bike I just bought to clean and make some maintenance on everything, I removed the seat/battery/etc the last weekend, had some struggle with the PRI position since I don’t know what full word it stands for so I kind of put gasoline everywhere,…anyway.

After taking all of these appart I noticed I got what looks like the gas admission for the middle carb that wasn’t connected to anything, I’d like to know what (I guess a tap) it’s supposed to be connected to, left or right tap or something else ? There is rust on it so I hope water didn’t get in there and damaged anything, there is come evidence mices have been living there so they might have eat what was supposed to be here.

If anyone has a picture from the top of the three carburetors with explanations that would be great.


Are you speaking of the 3 vacuum ports on the top of the intake?

Perhaps yes, I haven’t looked at the scheme yet but that may be it, the middle one was discand I don’t whether it’s normal or not

The middle port on my bike was capped off with a rubber cap. The left went to the left petcock and the right to the right petcock.

those ports are typically used for syncing the 3 carbs together, when not in use the middle port is just capped off.

1977 Yamaha XS750 2D Cafe Racer

Ok thanks :), I was wondering since the middle one seemed to have been ripped off and the right and left were linked to the two taps. I took a look at it this weekend and they are in fact located AFTER the carb, they are on the engine intakes, just so we are talking about the same thing.

Yep those are it

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