Coast enrichening circuit

[Sipper']

Why is this on the stock carbs?

[quarterliter]

Their is an enrichening circuit but its not for coasting its for cold starting. There is no choke just an enrichener

[Motofool]

Originally Posted by Sipper'

Why is this on the stock carbs?

Because the manufacturer of the carburetor, Keihin Corporation, decided to put it there.

http://faq.ninja250.org/wiki/How_a_c...a_Closed_Mouth

It is desirable to avoid explosions through the inbox and exhaust pipes during decelerations with closed throttle.

Lean mixes burn much slower than proper mixes; hence, explosion happens way later than the spark jumps inside the combustion chamber.

The expansive wave hits the exhaust and intake valves while these start opening (transition exhaust-intake strokes), continuing on into the mufflers and inbox.
This wave could damage those parts.

That little coasting enricher, senses the high rpms' of the engine and the strong vacuum (closed throttle) and injects extra fuel into the mix to make it less lean, avoiding the retarded explosions.

[Sipper']

Great explanation! Thanks.

[Motofool]

Originally Posted by Sipper'

Great explanation! Thanks.

You are welcome

A bonus:

Link to original page on YouTube.

Note that what we commonly call choke is in reality another enricher circuit, only that this one is not automatic but manually opened by us during start ups.

Same principle of making the mix less lean but two different applications and devices (coasting enricher and starting enricher).

Real chokes, which we don't have in our carburetors, choke the intake air, inducing vacuum over the jets and sucking extra fuel to enrichen the mix.