Had an interesting problem with the 2a yesterday. It had started refusing to idle - ran fine but needed the choke to keep running at an idle, even when hot.

I thought "I know what the problem is - blocked idling jet. We've been there before".

So bonnet up and back against the windscreen, disconnect aircleaner, choke, throttle and fuel line. Disconnect choke to throttle link and accelerator pump link. Remove four screws to allow the top to lift off, and take it into the workbench.

Turns out the idling jet is not blocked. The problem was that the two screws holding the emulsion block to the carburetter top were loose. This allowed the high vacuum at an idle to suck air, making the mixture too weak when idling. The leak was small enough that when the throttle was opened a bit and the vacuum reduced, the extra air was not enough to affect the mixture significantly. Put everything back together and it now ticks over like a clock.

This could be something to keep an eye open for.

John