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Where is my carb's vacuum port?

  • Thread starter Thread starter MrZig
  • Start date Start date
M

MrZig

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This is a diagram of my carb: http://www.cmsnl.com/img/partslist/carburetor-gsx400-1980-et_bigSUE0165FIG-12.gif

It looks like a BS32SS, however it's on my 1980 GSX400 parralel twin.

I need to sync the carbs as I took them all apart for cleaning, however to sync them I need both of them to have vacuum ports. The problem is the only vacuum port I can find is on the one that goes to the petcock. The other carb has nothing at that location.

This is my carb itself:


Click to enlarge

Where is it, or does it exist? If it doesn't exist, how do I sync them?
 
MrZig said:
This is a diagram of my carb: http://www.cmsnl.com/img/partslist/carburetor-gsx400-1980-et_bigSUE0165FIG-12.gif

It looks like a BS32SS, however it's on my 1980 GSX400 parralel twin.

I need to sync the carbs as I took them all apart for cleaning, however to sync them I need both of them to have vacuum ports. The problem is the only vacuum port I can find is on the one that goes to the petcock. The other carb has nothing at that location.

This is my carb itself:


Click to enlarge

Where is it, or does it exist? If it doesn't exist, how do I sync them?
Click to expand...
I don't see one in your photo. You should have a bolt on each intake port on the head that you remove and install a fitting for the hoses to attach to for synching.

You really don't even need gauges to sync a two cylinder. Set the idle up and remove one plug wire at a time and set the idle on each carb to match the other while the bike runs on one cylinder.
 
Last edited:
cruz del sur said:
Did you check the intake boots ???
Click to expand...


I just went out and checked, and although there's nothing in the boots themselves, there are screws on each end of the head, right beside the boots. I imagine these unscrew and you screw in vacuum ports?

Edit: ^^ That confirms it. Awesome, I was wondering what those were.
 
Billy Ricks said:
I don't see one in your photo. You should have a bolt on each intake port on the head that you remove and install a fitting for the hoses to attach to for synching.

You really don't even need gauges to sync a two cylinder. Set the idle up and remove one plug wire at a time and set the idle on each carb to match the other while the bike runs on one cylinder.
Click to expand...

Is this really a viable way to sync them?

Pull the plug on the non adjustable carb, note the idle speed, then put it back on and take the other side (adjustable side) off and set it to the noted idle speed, then rinse and repeat and make sure they're both the same?
 
MrZig said:
Is this really a viable way to sync them?

Pull the plug on the non adjustable carb, note the idle speed, then put it back on and take the other side (adjustable side) off and set it to the noted idle speed, then rinse and repeat and make sure they're both the same?
Click to expand...
That's the way Suzuki used to recommend synching the old two cylinder two-strokes. I had a T-305 and it always worked for me.
 
Billy Ricks said:
That's the way Suzuki used to recommend synching the old two cylinder two-strokes. I had a T-305 and it always worked for me.
Click to expand...

Neat, well I might give it a shot.

Here's another 'where is it' that's kindof dumb. A few days ago I was 100% ignorant on how carburetors work, and just sat down and read and read about them to figure them out. That doesn't stop basic questions from arising though.

When people say to adjust the idle speed, I'm using an educated guess that they mean to change the big throttle-stop screw, right?
 
That would be correct. Make sure there is a liitle slack in the throttle cable so when you turn the bars lock to lock the idle doesn't rise on you.
 
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