TOPIC: Amal 930 pilot jet mods

So after being stranded several times with crap in my idle jets, I sucked it up and pulled the plug out of the front of the Amal. Dave C. talked me through the simple procedure. A 4-40 screw threads into the plug and pulls them right out. A 10-32 tap and screw plugs the passage after cleaning. With the air screw removed, you can now put a piano wire down the idle jet and clean out the passage properly.

This procedure should work for all 900 series carbs. I have done this myself on 930 and 932 several timesover the last 20 or more years. This is to do a "real clean" cleaning. Otherwise you will often be doing an idle circuit cleaning several times before you get happiness and have removed the little piece of crap that has plugged the idle jet.
The new amal "premiers" have mostly done away with this procedure, but on the premiers you still have to take the carbs off the head to unscrew the new style idle jets.

I upgraded the carbs on my 75 a few years ago, it turned out the seller did not set them up for a MK111. I put everything to the original settings, correct spray tubes, jets etc., and it starts, runs and idles as it should. Kick starts right up from cold with the choke closed. No issues on the trip to Michigan and back. Now that FUC#ING SPEEDOMETER DRIVE!!

The new premiers have been shipped with .017 low speed jets, improperly called idle jets..why is that????
The "as sold" premiers have been very often found to need .019 which is closer to conventional old MKI concentrics...

In my life long education since leaving high school, I learned what an analog computer was and how it differed from a digital computer. FACT: A carburetor is an analog computer. Just like a digital computer garbage in=garbage out.

This was reinforced the other day when ?Kara asked about dellortos. some one gave the link to a dellorto manual. I cruised through it to see the quality of the write up to compare with the amal pamphlet. I was very positively impressed at the slightly more description of the idle/low speed circuit.
The dellorto write up includes what I call "bleed" and "feed"(they call progression). The low speed function acts in two modes.
The low speed circuit has 1 fixed size fuel jet and 3 air holes.
The main idle mix orifice is on the engine side of the throttle slide. It passes fuel and air mix sourced from the carb face open passage but idle mix air volume is controlled by the idle air needle screw.
In addition to the 3rd hole/3rd hole is in front of and is immediately on the outside of the slide wall.

Next the 3rd air hole works first in bleed mode when the throttle valve is shut down to the idle position. Atmospheric air enters the hole in bleed mode and goes in the "mixing chamber" to complete the fixed fuel jet idle air mix ratio.
The air is from the adjusting screw AND blended with the 3rd air hole inside the mixing chamber(little round aluminum slug in body.
The big AH HA
2nd next 3rd air hole act in progression or feed mode. Since the call for more speed, you raise the throttle there is now vacuum on the exterior of the 3rd air hole.
The idle/low speed fuel jet goes into full feed mode.
If the 17 is not enough in low speed mode it however will still work OK in idle mode by adjusting the needle.
If you run a richer 19 jet the performance is no longer limited/starved in feed low speed mode and can be adjusted for idle mode with a different air screw setting.

All of this analog functioning is to allow running up to the HIGH speed circuit which then takes over.
The dual mode port definition makes it easier for me to comprehend it's functioning. Seems simple enough to me why the 17 might be lean and the 19 is better .
The ignition advance setting actually is very influential to idle speed/vacuum so it can easily explain differences out side of carburetion parameters