air screw adjustment

[countrytn]

does anyone know the amount of turns for the 4 air adjustment screws on a 01 Yamaha 115 TLRZ 115 2 stroke

[boscoe99]

Yes. Of course.

[Yamaha 50TLRA]

I dont know for sure about yours but from my experience in all the past outboards I have had they all averaged about 1 1/2 turns out from completely seated in and then fine tune from there.

My 02 Yamaha 50tlra is 1 3/8 - 1 5/8 out

[almetelo]

5/8 turns out after lightly seated +/- 1/4 turn (if I'm not wrong)

[boscoe99]

5/8 turns out after lightly seated +/- 1/4 turn (if I'm not wrong)

We have a winner.

Free chicken dinner.

[countrytn]

thanks guys, every screw was at a diff setting

[almetelo]

Chicken!!! Again!? lol

To make sure burning (A/F) is good have look on spark plugs, diferent settings doesnt mean is wrong)

[rodbolt17]

double chicken dinner.
those screws DO NOT alter A/F.
I win.
I prefer beef.

[boscoe99]

double chicken dinner.
those screws DO NOT alter A/F.
I win.
I prefer beef.

What does the adjustment do?

[countrytn]

What does the adjustment do?

I want to know also

[boscoe99]

And since it does not affect the air/fuel ratio why does Yamaha install an anti-tamper EPA plug?

Is this the screw of which you speak?

[countrytn]

yes that is the screw, mine don't have tamper covers

[boscoe99]

Early engines did not have the plug. Later models got it.

Thanks to the EPA.

Who did not want folks changing the idle RPM air/fuel mix to get their models to start and run better.

[TownsendsFJR1300]

2001 115TLRZ Yamaha Outboard CARBURETOR Diagram and Parts

Part 20 , per the above parts manual is: "screw, air adjusting".

IME, the adjustment screws, closer to the intake( between the butterfly and intake manifold) adjust the amount of fuel to be released/adjusted while at low speed.

The adjustments are generally for fine tuning low speed, idle. In the higher RPM's, the main jets take over for the overall A/F mixture.

However, I'll bite as well..

[rodbolt17]

I know what it says, Yamaha also calls the 3 switchs in the oil tank a sensor.
the translation wasn't so good.

if you carefully study the design of that carb you will notice it has a set of back draft jets as well.
no one in any class ever mentions them as most don't understand the principle.

anyway back to the idle circuits.

you will notice the carb has a PILOT(idle) air jet AND a PILOT fuel jet for each venturi.
this controls the air to fuel ratio.
the adjustment screw simply allows more or less of this mix to pass.

its why if all else is correct you can set them at the factory spec and it works.

not all carbs work this way but most the twin float and most carbs that use a pilot air and pilot fuel jet will.

unlike the old jonny rude carbs that simply ran an orifice tube for fuel and a pilot (idle) air jet.
those we typically had to play with jet size to get a stable idle.

remember, its not engine vacuum that moves fuel, its that 14 mile coluom of air pressure on the fuel in the bowl that moves fuel.
don't belive it, change the air pressure in the bowl.