what is best rpm for pilot screw adjustment?

[laflaone]

Have a 9.9MSH 2-stroke, built in 2008. When adjusting the fuel/air ratio with the pilot screw, what is the best engine speed to do this? Idle, mid range or full throttle?

[boscoe99]

The pilot screw is Yamaha's term for idle mixture adjustment screw. Setting should be done at idle RPM.

[laflaone]

Every 2 stroke carb I can remember has two mixture adjustments: one for idle and one for higher RPM's. If the pilot screw is just for idle, is there one for the higher RPM's?

[rodbolt17]

no manufacture that imports or is made in the states has used a high and low speed mixture screw since at least the mid 1970's.
most went to fixed jet on both low and high speed.
if you still have a mixture screw it should be set at idle.
as your carb is EPA on that 9.9 then start at 1.5 to 2 turns out.
based on the last year specs were avalible.

[laflaone]

Thanks for your replys

[boscoe99]

Idle RPM spec for that motor is 750 plus or minus 50, when in neutral. 650 plus or minus 50 when just into gear.

Idle mixture is 1.5 turns out from slightly seated, plus or minus 1/4 turn.

Per the Yam tune up spec book.

[laflaone]

Idle RPM spec for that motor is 750 plus or minus 50, when in neutral. 650 plus or minus 50 when just into gear.

Idle mixture is 1.5 turns out from slightly seated, plus or minus 1/4 turn.

Per the Yam tune up spec book.

Thanks. I downloaded the service manual, and it is very helpful.