What are all the functions on a carb

[Yamaha3535]

I have a 2003 yamaha 130 txrb and I'm a newbie as you can tell. I wanted to know how a carb works and what all the jets and screw do on my carb. I have attached the parts diagram of the carb. If you could tell me what each jet,screws and everything else function would be awesome.would really intersted in #s 20,16,14,12 and 9. Thanks


2003 130TXRB Yamaha Outboard CARBURETOR Diagram and Parts

[99yam40]

You got to be kidding

[rodbolt17]

its fairly simple
the pilot air jets simply let in air at a known quantity.

the pilot fuel jet lets in fuel at a known quantity.
the main jets let in a known quantity of fuel.
the jets under the plate are bowl vent jets.
not shown but they exist on most carbs of that design.

the mixture needle screws don't alter air to fuel.
air to fuel at idle is fixed by the pilot air and pilot fuel jets.
all they do is allow more ore less of the A/F mix.

stupidly simple carbs that work very well.

any other questions?

[boscoe99]

its fairly simple
the pilot air jets simply let in air at a known quantity.

the pilot fuel jet lets in fuel at a known quantity.
the main jets let in a known quantity of fuel.
the jets under the plate are bowl vent jets.
not shown but they exist on most carbs of that design.

the mixture needle screws don't alter air to fuel.
air to fuel at idle is fixed by the pilot air and pilot fuel jets.
all they do is allow more ore less of the A/F mix.

stupidly simple carbs that work very well.

any other questions?

Yes. I have a question. It sounds as if the final fuel/air mix at idle cannot be varied. Is that really the case?

At idle the throttle is opened slightly to allow air for combustion to enter the intake manifold. At the same time air proceeds to flow through the pilot air jet and is then mixed with fuel from the pilot jet. The air/fuel mixture then goes through other parts of the carburetor, is metered by the pilot screw, and then flows into the carburetor behind the throttle plate.

If the pilot screw is opened such that an additional quantity of the air/fuel mix is delivered to the motor, while the basic volume of primary air flow is fixed, then is not the idle mixture enrichened?

[Yamaha3535]

Thanks for explaining. I had an idea but didnt know exactly which jets did what.