Quick Amal Mk2 question

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May 11, 2007
Are either of the red circled passages supposed to be blocked off?

Quick Amal Mk2 question

Both of mine are open, but I've seen pics of the left one both open and blocked off. I only ask because it looks like that's the passage that leads to the idle jet mounted in the carb body, which seems like it wouldn't be much use then if the airway was blocked off.
I have a right hand mk2 on my bench. The holes are, looking from the rear:

Left hand: blanked off with a plug ( although it looks like it has a small hole up the centre).

Middle : goes to the needle jet

Right: goes to the pilot jet.
Off memory;
One side should be blanked the other open depending on what hand the carb is, and the centre should be fitted with an aluminium air jet.

Not totally sure about the Mk2?
But for the Concentric Mk1 the blocked off passageway is on the opposite side to the pilot air screw, so on a *left-handed* carb that has the pilot air and throttle stop screws on the left, the right-hand passageway will be plugged (as the R/H side then becomes the fuel passageway) and is the opposite way for a right-hand carb, which is plugged on the left.
Ok, makes sense now. Not quite sure why this one had both open but it's probably the cause of some of the idle problems I've been having, seeing as though I could only meter half of the air for idle coming through.
I'm still unsure of what the benefits are of putting the jet in the carb body opposite the idle airway as opposed to in the float body though. I know it can really go either way, but does anybody know the actual reason for using one or the other?
The jet in the carb body is usually for two strokes, however Amal reckon it can be of help in that position on some four strokes.
The Air Jet in the centre drilling controls the depression in the primary mixing chamber ie it has an effect over the main jet. Whereas the side drilling air supplies the pilot circuit and is metered through the air screw and doesn't need a jet. I think the Mk1 has only two drillings with only one open and it supplies both the primary mixing chamber and pilot circuit.
I've got a book on the Mk2 and Mk1 Amals some where so if you think that's twaddle I'll dig it out to check.

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