'90 Carb vacuum hose question...

[wcj]

Just a quick question since I cant seem to find the answer in the Haynes manual and the Clymers I ordered isnt here yet.

On a '90 750F, does the vacuum fitting from carb #3 go to the vacuum fitting on the petcock?

Clarification: Carb #3 is defined as the 3rd card from the left if you were sitting on the bike normally.

I ask because the fitting is broken off of carb #3.

I just bought the 750 and Im going through it and troubleshooting a possible fuel delivery problem.

• The bike would start, but it wouldnt stay lit unless you throttled it.
• It also appeared the PO was running it from PRI to deliver fuel to the carbs.
• It also had a pretty bad fuel leak from the lines so those have been replaced already.
• Choke cable was perma stuck and wouldnt budge

Here's what Ive done so far:

• Replaced fuel lines
• Disassembled and cleaned the petcock and replaced internal o-ring
• Ordered new choke cable

I havent cleaned the carbs yet since I want to get it to run consistently (even if rough) before I tear it down anymore. Anything else I should look for?

[Sin]

number 4 far right side

[wcj]

number 4 far right side

Use the fitting on the bowl cap for carb #4?

Isnt that the same carb that has the vent fitting (on the side) that goes to the fitting under the tank as well?

[Sin]

no its on the right hand side its a alum nipple molded into the carbs all the carbs have the nipple just number 4 is drilled thru to the inner throat to pick up vac

[wcj]

no its on the right hand side its a alum nipple molded into the carbs all the carbs have the nipple just number 4 is drilled thru to the inner throat to pick up vac

Ok. So the fitting I referenced as a vent fitting on #4 is actually the vacuum fitting that needs to go to the petcock, correct? That means when I get the new bowl cap for #3, just block off the fitting on the cap?

[Sin]

yeah you got it the carb tops black plastic are the sync ports for synchronizing the carbs once its running its just a vacuum cap

[wcj]

yeah you got it the carb tops black plastic are the sync ports for synchronizing the carbs once its running its just a vacuum cap

Excellent. Thanks.

So that leads me to another question then... what goes to the fitting under the tank (near center of tank)?

[Sin]

vent and drain for the gas cap in case you over fill it

[wcj]

Again... many thanks.