NT Carb.... No air adjustment

[motorpsycho]

Gh0stRider is right. I have seen this done "factory" on a 197x jawa pionyr 50cc moped (czechoslovakia made, well really it was more of a scooter but that makes no difference here). No idle a/f adjustment, there was a tiny hole in the bottom of the intake manifold right after the carb, the hole pulled air in right from the outside with no filter. If you plugged the hole with your finger while the engine was idling the engine would eventually die and be hard to start after (flooded). I have seen many of these scooters "back in the day" and they ALL had the tiny hole in the intake manifold. Didn't hurt anything, the manufacturer has been building bikes for maybe 70 years (mostly 2 stroke) so I assume that they knew what they were doing.

well, see that's a bit of a different set up because there is no idle adjustment screw...just the air bleed on what you are talking about.
what he was talking about was drilling a hole in the intake and running an adjustable regulator off of it, so he could open and close the hole whenever he wanted more or less air, while still having the idle adjustment screw funtional.
his idle adj. screw would still be in place and still be used. he would be able to lean out the motor by opening the regulator so it would suck more air.
what you are talkin about is used often on 2 stroke go kart race engines...the air bleed idea with an idle adjustment. but, in the case of the 2 stroke karts, they can richen /lean out the mixture by adjusting the air bleed on the fly from a control on the steering wheel. they can also advance/ retard the timing in the same way from the steering wheel. f-1 cars and indy cars have the same sort of set up (but FAR MORE advanced).
2 stroke shifter race go karts are not THAT far behind the technology that an f-1 car has to be honest. it's just on a much smaller scale, and at a much lower speed.

 

[danlandberg]

The NT carb idle screw is just a slide/needle stop. It keeps the slide from dropping down to far. Which would choke the engine (no air/fuel). It dose not introduce more air or fuel into the combustion chamber. The only mixture adjustment is the needle and slide (Raise the clip on the needle you get less fuel & more air & visa verse) The only other adjustment would be to change jet size. My thought was to introduce an air bleed using a tapered screw from a VW carb or another source. So I could allow a very small amount of air into the system. Once tuned properly there should be no problem through the entire throttle range!

 

[motorpsycho]

The NT carb idle screw is just a slide/needle stop. It keeps the slide from dropping down to far. Which would choke the engine (no air/fuel). It dose not introduce more air or fuel into the combustion chamber. The only mixture adjustment is the needle and slide (Raise the clip on the needle you get less fuel & more air & visa verse) The only other adjustment would be to change jet size. My thought was to introduce an air bleed using a tapered screw from a VW carb or another source. So I could allow a very small amount of air into the system. Once tuned properly there should be no problem through the entire throttle range!

yes i know that...all the idle screw does is raise / lower the slide in these carbs.
I have been thinking about your idea, and it's starting to make more sense.
actually, i have a 1974 kawasaki 2 stroke, and it has an air bleed set up for the choke on the carb. the air bleed is controlled by a lever on the left side of the handlebar. it is a small hole in the intake and it has a small rod that opens and closes as you move the lever. the rod is sealed on each end with 0-rings.
But, after the engine is warmed up and you are riding...if you open the air bleed, it will kill the engine because it's getting too much air.

 

[danlandberg]

Is this Kawasaki a street bike (3 cylinder 2 stroke?) And are you sure that the lever is opening the air bleed circuit? or closing it? If it"s the choke lever it would be shutting off the air (choking) like all normally aspirated engines, less air to fuel for cold starting. Fuel injection is different! Some 4 & 6 cylinder engines have an extra injector (computer controlled) to add more fuel to air for cold starts. And on throttle body injection, The computer keeps the injector(s) open longer at cold start. (More fuel to air) until operating temp is reached.

 

[motorpsycho]

it's a 1 cylinder, 2 stroke, rotary valve 100 c.c. on/off road bike.
it has oil injection (for the 2 stroke oil) and is carbureted.
yes, when you "choke" the engine, it closes the air bleed for cold starting.
after the engine is running and warm, you can open the air bleed. they refer to it as a choke, but it is not like a choke where it has a butterfly or an obstruction that opens and closes in the throat of the carb. the air bleed is in the intake manifold.
this would explain why when I think i am "opening" the air bleed based on the movement of the lever after it's running, I am actually closing it...cutting off the needed air for it to run.
choking the engine closes the air bleed, un-choking the engine opens the air bleed.