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[windmill john]

There I was, kicking for England this morning and eventually Gupta started.

On the ride to work I was thinking to myself, why is it that if I use full choke but twist the throttle, technically the same amount of air passes through. But... starting is easier if I do not use choke.

I then realised why. The Amal choke blocks off the central part of the inlet. This will have a big effect on the vacuum or sucking of fuel from the needle jet, as the choke mechanism is blocking the direct air path.

I can understand why this causes issues. An airflow either side of the choke slider will not suck up fuel properly from the bowl. I guess a richer setting to the needle or cutaway would compensate, but it looks like with my settings, I need more of a suck over the jet.

There has been times I've needed full choke and no throttle. That confirms.... I'm running a little weak with my settings.

It's not a question, just an observation.

[trophyvase]

I realise this wasn’t a question – but!

A choke relies on reduction of air to create a rich mixture – while a starting jet relies on an increase of fuel to create the rich mixture needed for starting. Two entirely different systems to produce – hopefully – the same effect: an engine that starts in adverse conditions.

[trophyvase]

PS – in both cases the theory is that the throttle should be closed to produce the required effect.

[PeteF]

Properly adjusted any engine should start with the throttle closed.
Having said that I know they're all different.
Generally though, twisting a handful of throttle as you kick is usually counter productive.

[windmill john]

I find that when stone cold, not touching the throttle at all starts the best.
When warm, it needs a blat of throttle.