350 Carb Air Passage Info

[moonpup]

In the pic below, you'll see 4 openings that are cast into the front opening of our carbs, 3 at the bottom & 1 in the upper right quadrant.

During my various carb cleaning/refurbishing projects, I've figured out the purpose of each passage...... with the exception of the bottom right opening.

Looking at the underside of the carb, it appears to go all the way across the carb and possibly into the little brass tube located on the other side. Any attempts to blow air thru it left me with the impression that there was a blockage somewhere and all attempts to clear it were futile.

That wasn't going to work and I needed answers, so using an extra carb body that was already trashed out, I got my dremel tool out and went to work! Starting about in the middle of the carb, I began to grind off the top of the passage and head towards the brass tube. Finally just before reaching the tube, it ends with NO opening to any other passage. That's it... a dead-end passage of no use for our carbs.

So now when y'all clean your carbs, no need to worry about that passage being clogged! Happy days! 

[hardy]

Great investergating there mike! My thinking is the carbs came out of a standard mould and could be adapted for left hand or right hand air screw adjustment depending who the end customer would have been?

My wife’s 69 Kawasaki samurai 250 has the same carb in a 22mm SC (clamp on) variant.

Hardy

[BRT-GTR]

            Nice ? work mike, like many I investigated the carb passageway drillings and paths when I had the idle/airscrew problems last year but didn't have a carb body I was prepared to destroy.
          Would you care to take the destruction of that carb body one step further and cut a cross section across the idle air screw seat, that we were discussing the other day.Ie the cross drilling between the two bottom left carb drillings. That would show us how delicate/robust the air screw seat is and maybe a better solution to repairing them.
            Brian.

[moonpup]

Ryan.... I had considered the that possibility, but since this side had the brass tube at the end of the passage that the other side didn't have (or even the casting for it), I had to be sure.

You are right though about the "standard mold" and the "adapted for left hand or right hand air screw", as the casting for an air screw on the right side of the carb sticks out like a sore thumb to me now! 

Brian.... Great idea on the cross section! I'll get right on it and get back to y'll if I'm successful.

UPDATE - cross section can be seen in this thread...  http://bridgestonemotorcycleparts.com/index.php?topic=4613.0