Unknown Needle in Trottle Plate Area Kei Hin 34

1981 KZ750 LTD H2 4cyl

While checking the throttle plates today, I noticed a needle sticking down on the #2 carb. It pokes out from the top and goes through one of three small holes in the top of the carb throttle side. I attached 3 pictures of it below. It has clearly dented the throttle plate just a bit. This is the only carb that has this feature, and it doesn't seem good. I can prop up the pin and the plate will shut enough that the pin will not come out, but only when the carb is on its side. This means when it is on my bike, the pin will always fall.

This is not in any diagram in my Clymer. What does this mystery hole do?

Thank you in advance...


The needle comes down exactly where the throttle plate crosses the top of the carb effluent.


On the top side under the rubber diaphragm is a capped off hole, as seen in dead center and just to the right of the air fuel mix screw.


A blow up of the holes in proximity to the throttle plate resting point.

That group of 3 small holes is where the gas from the pilot system exits the carb and enters the motor. They should be totally clear. No needles. The throttle flap/buterfly/plate when fully closed should close at or on those holes - see your other carbs.- without obstruction. Obstruction may make proper carb synchronization difficult




Can that needle tip be removed without damaging the hole? I dont think you want to enlarge the hole.

Is it possible it was left over from an attempt to clean by a previous owner ? I wonder if it might be the tip of a pilot screw (#1 in the diagram above) which a previous owner broke ? If it is small enough it might be possible to get it out by removing the pilot screw (with o ring, washer and spring) and by using compressed air and shaking.

The pilot screw is ~5mm forward of this. The middle pic above has the top view. It is under the silver cap in the center of the pic. I do not have any replacement caps, so I didn't want to go popping this out.

There was one pilot screw that was missing the needle tip when I replaced the A/F fuel screws.

The pilot screw is ~5mm forward of this. The middle pic above has the top view. It is under the silver cap in the center of the pic. I do not have any replacement caps, so I didn't want to go popping this out.

There was one pilot screw that was missing the needle tip when I replaced the A/F fuel screws.

Yes
I totally understand where the pilot screw is located in relation to the 3 small holes (by pass outlet. #3 in the schematic in my post above). I have the same carbs. I am not suggesting that the needle in question is the tip of the pilot screw. My point was that previous owners have been known to bugger up pliot screws and possibly a pilot screw tip was broken at some point in time and became lodged 5mm or s back in one of the 3 holes. If the mystery needle was inserted from underneath where we can see it then it should come out that way. If it became lodged in the hole from the top then it becomes more difficult.

Regarding the "mystery cap" in your middle photograph in the first post I dont believe this is a "cap". I am guessing that it was a opening that was sealed after the various passageways and holes were drilled during manufacture.
I would not dare suggest that this be drilled out .

Could this be the a/f bypass outlet? Since I did find a broken a/f screw that was missing the needle (I took my readings on rotations of a/f screws very carefully) when I replaced them, it could be from the prev owner. Going to try taking out the a/f screw and shaking it back out the passageway. Okay, tried the shake around a/f and nothing came out. The needle that once appeared no longer appears, but I think that is due to having it shaken all around.