Pilot screw adjustment questions

[Bud_man]

Hi All -

Many thanks to all that have created this great source of information.

After searching the archives here and consulting my service manual, I have successfully removed, cleaned and replaced the carbs on my C90 yamaha. During my in-water test run the motor ran better than ever. However, I have since read that I should have "fine tuned" the carb using the pilot screw and the 1-1/4 turn is only the starting point (us newbies - ugh). However, I have a few questions

Realizing I adjust the pilot screw with the motor in water, warm engine, in gear, at proper idle speed.

1. Should I turn the pilot screw on each carb a 1/8 turn and wait to hear for idle speed increase, or adjust all the carbs together - turn all three carbs 1/8 turn in, then wait? In other words should all three carbs have the same turns or are they independent adjustments?

2. Will the proper adjustment likely be +/- 1/2 turn from the starting point of 1-1/4 turns out? (more - less?)

3. Once I find the peak rpm, should I open the pilot screw 1/4 turn for the final setting?

Thanks again for your help.

Bud

 

[w2much]

Re: Pilot screw adjustment questions

1) I do each carb seperately,til they all run smoothly if no flometer is available.
2)Probably out, richer is better than leaner.
3)Yes, richer is better than lean.
Good Luck

 

[bowhuntrrl]

Re: Pilot screw adjustment questions

1) I do each carb seperately,til they all run smoothly if no flometer is available.
2)Probably out, richer is better than leaner.
3)Yes, richer is better than lean.
Good Luck

On Suzukis, out is leaner not richer. I'm not sure about Yammies.

 

[rodbolt]

Re: Pilot screw adjustment questions

best I remember the 3cylinders usually dont have an idle air jet. screw it it to lean it and out to richen it. however its been my findings that if all else is correct it will run at the specified setting +or-1/8th turn.
on the V models that use an idle air jet and an idle fuel jet the mixture screw simply allows more or less of the mix.
thats why its imperative to identify each carb circuit and uderstand its function.

 

[Ray Neudecker]

Re: Pilot screw adjustment questions

Yes many three cylinder models do have idle air adjustments. Otherwise Rodbolt as usual is right on the money.