nevhunter wrote: Sun Jul 20, 2025 2:31 amwhen I mentioned finish it was ... where the needle runs and where the Metering is done

Ah, sorry I misunderstood. Oh well, at least it prompted a calculation that someone might find useful or interesting.

I still don't get the need for the middle bore. As a possibly-relevant aside, I already noted in a previous post that Mikuni's needle jets are spaced every 0.0002", indicating that changes at a level of ~0.0001" have a measurable effect. Motivated by that, plus having assembled an instrumentation ...

The surface finish will certainly affect the flow rate. The annular area between the 2.50 mm (0.0984") needle and the rough walls of the 0.125" hole is nearly 4× larger than between the needle and smooth walls of the 0.106" metering-portion of the jet, so the effect of those rough walls on the flow ...

If you've ever been curious what the inside of a pre-Monobloc needle jet looks like (and who among us hasn't spent many sleepless nights thinking about this?), feast your eyes on the two photographs below.

As the first one shows, the annual area between the jet and needle that determines the flow ...

if an old jet orifice/needle can be accurately measured I don't see much of an issue. There's no issue at all with old needles and needle jets, since the flow depends only on the annual area between them. If measurements show they have the as-new OD and ID, they'll work just as well as ones that ...

FYI, I have a "collection" of ~30 used brass and steel Amal Standard-type needle jets, and the following photograph shows at least 16 different types/sizes of jets were made.

Amal_Standard_NeedleJets.jpg

Since some of the writing will be hard to read, from top to bottom the markings and ...

Since this thread originally was about flooding, I thought it would be useful to show the tool I made when I was preparing my 1928 Ariel's pre-Monobloc carburetor.

Amal_Standard_FloatLevel.jpg

In case it's not apparent, the function of the clear tube is the same as is shown for a GP in a Gold ...

It's only NOT rocket science if all parts are in known good order Engines are amazingly forgiving, continuing to run (albeit, badly) with a worn carburetor, valve timing not set correctly, incorrect valve lash, dodgy magneto, etc In most cases, a carburetor can be assembled with components from the ...

Removing the plug and it is black and sooty … The pilot air screw is about right, cutaway is what it is, main jet is whatever is standard, but first thoughts would be to lower the needle. This sounds very much like the symptoms of a worn needle jet, since most riding is done at fairly low throttle ...

if fuel was suspected to be passing from the float valve, then I guess that is the first thing to investigate as likely that would be the root cause rather than the fuel level. Quite right. Since most of us lack x-ray vision to see what is happening inside the carburetor, that hole serves a very ...