swapping carbs, where did my vent go?

Trying to swap out the carb on my DRZ S becuase mine was gummed up. I bought a used carb from a DRZ, not sure of model and had it rebuilt. It was not an E so I pressumed it would swap directly. After I get the thing hamboned in there I realize the lines are not the same.

The new(er) carb does not have a vent line to return back to petcock, originating from same location as the original.

The new(er) carb does have a vent line at the right rear (behind throttle linkage), going straight down 4-5 inches and terminating.

What is this other line?

What do I do about not having a return vent for my petcock? Isn't this line needed to keep the fuel flowing? (I really liked the stock carb/petcock and don't want to fiddle with turning off a gas vale after evey ride...) Both are Mukini carbs and look identical, except new literally does not have holes drilled from factory where the vent would have been.

:banghead: :banghead: :banghead:


you need the vacuum line. its in the head...

the vacuum line goes from the (non fuel) fitting on the petcock to one of the two bolts on the side of the head. you take one of those bolts out and put a vacuum fitting on there. thats how the gas gets pulled from the tank...


too lazy to take my own picture. the two bolts are side by side on the head. just about straight down from the red arrow...

is this what youre asking?


First, to clarify, the line you are missing is not a vent, it is a vacuum hose to operate the fuel petcock. As far as I know, every DRZ400S and SM sold in the US, the carb has the vacuum connection. I can not quote the year of change but the 36mm Mikuni was also used on CA E models and eventually all E models. I have not seen the Mikuni on the E models so I don't know if they used a manual or vacuum operated petock. Assuming the carb you have is otherwise correct, you can add a vacuum nipple to the head to operate the petcock. Either of the bolt locations shown in the picture will work for a vacuum connection. You can buy the nipple for an E model that used the Keihin FCR carb.

what happened? this happens a lot doesnt it? people figure out their problem and never come back?

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