what/where is the choke feed?

[Alex M]

is the choke circuit pick up tube part of the choke feed?

is the starter plunger part of the choke feed?


i've taken my carbs apart with the carb rebuild PDF. i'm slowly starting to understand what everything is, step by step....

thanks

[tkent02]

is the choke circuit pick up tube part of the choke feed?

is the starter plunger part of the choke feed?


i've taken my carbs apart with the carb rebuild PDF. i'm slowly starting to understand what everything is, step by step....

thanks

Not sure exactly what you are asking...
The choke plunger is just a valve that lets in an emulsion.
The emulsion has it's fuel supplied through that brass pick up tube with the little holes in the side, which sticks down inside a small bore in the float bowl itself...
The passage to supply fuel to this bore has a very small orifice and can get clogged up.
Dip the bowls too and ensure this passage is clear with a shot of carb cleaner spray.

[Steve]

I know what you are asking, but I want to make sure we are on the same page with terminology.
The "choke" circuit in our bike carbs does not work like a choke circuit in an older car carburetor.
In a car carb, there is a flap that covers most of the intake to the carb, literally "choking" it down.
This increases the vacuum below that flap, which draws more fuel than usual through the jets, enrichening the mixture.

In our bike carbs, there is no flap that chokes the intake. When the "choke" knob or lever is activated, a plunger moves, exposing an alternate fuel path.
This is where the plunger lives, in the large hole in the center:


Gas is drawn up what you are calling "choke circuit pickup tube". It is the brass tube in the right front corner here:


You can see in this shot how the gas goes up the pickup tube to the back of the plunger:


Upstream of the plunger, filtered air is available under the diaphragm. After the plunger is pulled out of the way, this opening is where the enriched air/fuel mixture flows to the engine:


Seeing how dependant the system is on high vacuum, you might now understand why it won't work if you open the throttle while trying to start using the "choke".
Once the engine starts, simply adjust engine speed by modulating the "choke" knob or lever to keep the engine speed down to reasonable levels.

Note that I also tend to use quote marks when I talk about the "choke" system on the bikes.
That's because there is no flap to choke the intake, it is an "enrichenment system".

.

[Alex M]

wow. reading that was enlightening!

i know i have, in the past, had the choke pulled up AND twisted the throttle. the bike wouldn't start, and i was desperate.

now it makes sense. thanks steve for taking the time to post the photos and explanation!!!!

[Steve]

... now it makes sense. thanks steve for taking the time to post the photos and explanation!!!!

That's what we do here, for those that are really interested in learning.

Some are afraid to ask what they feel is a "dumb question". This it the type of answer they could receive, if they would only ask.

.

[trippivot]

enrichener - starter - choke all same term

best to say enrichener circuit. the lonely brass tube on the engine side of the carb jutting into its own little hole in the bowl is the fuel inlet for this totally separate fuel circuit. creating vacuum when the air inlet from the main venturi is exposed as the plunger is moved from it's closed position to the open position drawing up the fuel.


a "choke" is just a flap stopping most air going into the engine raising the vacuum and drawing more fuel thru the main/pilot jets.

old carbs had a "tickler" that pushed the float and flodded the main venturi -started a bunch of leg fires too.