NT Carb.... No air adjustment

[Gh0stRider]

Not good advice. Besides other considerations, GhostRider, you set out to cure a lean mid-range condition, not a rich one, which is Dan's problem.
Also, as you say, you only affected idle mixture with your mod - that's not what Dan wants, although in reality it will slightly affect the mixture at all throttle openings, of course.
Dan wants heaps of air, so that it noticeably affects the mid throttle range.
Your trick worked for you at idle, but with enough of a leak to do what Dan wants, there's the potential to cook the top end.......

Actually read what I wrote and you'll find that I did not set out to cure a lean mid-range condition.

What is it with you aussies anyway? Fabian and Hajuu and now you? Geez.

I'm jettin' outta here. Good luck y'all.

 

[AussieSteve]

I wasn't as accurate as I could have been, this is what I was referring to.

Moving the needle lower would fix the idle but cause an overly lean condition at mid throttle.

I should have said that you set out to cure a different problem to Dan's. That was my point.
You could have corrected me a little more politely, but it sounds like you have a bee in your bonnet.
The rest of what I said still stands.

What is it with you? If you have a problem with other people, take it up with them.

 

[danlandberg]

Thanks guys! After break in I am almost always at WOT. Every thing here is far and in between! (BFU). I am a person that likes to get from point A to point B as soon/fast as possible. (Get it done) But the faster I go, the more fun it is!!!! The intake leak was just a thought (from a while back) just brought it up for input. Thanks guys!

 

[Gh0stRider]

Dan,

I PM'd you with some tuning tips and another little trick to get a pretty fine adjustment of the air bleed. Let us know how it works for you!

 

[motorpsycho]

Give it a try then! You won't be disappointed.

Every carburetor that has an air bleed screw for idle mixture has an "introduced vacuum leak" - but the key is that it is a controlled vacuum leak, not one introduced by a bad gasket or a hole drilled in an intake. These air pump valves can be adjusted so the air introduced is a infinitesimal amount. Just enough needed to get things running crisply.

These ultra simple generic Chinese engine carbs do not have any adjustment for idle mixture, they don't have a dedicated mid range circuit other than the jet needle in the needle jet and a main jet that seems to be lean for EPA considerations.

My fix was to keep the jet needle high enough to allow for a good mid range (no lean bogging) but the idle mixture was too rich - so I corrected that by introducing a controlled amount of air through the aquarium valve and balanced the throttle stop and air bleed to provide a nice smooth idle. The setup is like a motorcycle carb where you must go back and forth to balance idle speed and a/f mixture with the two adjustments.

These simple carbs do a good job out of the box, but can be made much better with some simple, common sense modifications.

I can't give this a try even if i really wanted to. My engine does not have an intake manifold...the carb is bolted right to the cylinder.

 

[danlandberg]

Do you any pics of your set up? It might be what I'm looking for! (drop the carb & stay clear of the clutch cable)!!

 

[motorpsycho]

if you are asking me, no, i don't have any pics right now.
It would take alot of woirk to get the carb off of my engine because it is attached to the cylinder with long studs & nuts. the nuts sit in recesses in the back side of the carb, and you can not get a wrench on them to get them off. theonly way to get my carb off would be to drill out the ends of the studs through the nuts.

 

[danlandberg]

Is it 2 or 4 stroke?

 

[Dilly Bar Rob]

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.

 

[motorpsycho]

Is it 2 or 4 stroke?

mine? it's a 2 stroke, 50 c.c. slant head.