Mikuni SBN "Lightly Seated" Pilot Circuit Screw

[Pwnage1337]

I'm going to do my best to explain this because my carburetors are still on my machine.

The question I have is:

Why is it when turning the screws clockwise to get them into the lightly seated position, once they're lightly seated, The ears of the screws are not in the same position? Theoretically they should match, no? One of mine is almost perfectly perpendicular to the carb body, and the other is not.

On one of mine it seems like it goes in about an eighth of a turn further than the other one. Because of this, When I turn them one full turn out the screws do not look the same between the carburetors.

I'm trying to track down the source of my mismatching plug readings. My PTO is a nice mocha Brown and my MAG looks maybe a touch rich. At this point in time I cannot recall which is which.

 

[racerxxx]

They won't be the same. Zero guarantee the tap catches on the same spot on every carb. That's why you bottom out and reverse X.X turns from bottom. The bottom is your zero reference.

 

[racerxxx]

Also, they don't care where the cross shaft is in relation to the threads...... Because of the zero reference.

 

[Pwnage1337]

Thank you for the clarification.

 

[Pwnage1337]

The boat is running absolutely perfect so I am just going to keep riding it. The difference in plug wash is not super significant, just enough to bother me lol

 

[AKnarrowback]

What machine is this?

Rotary valve motors, at least on sleds, have a tedancy to run a hair richer on one side due to the rotary valve. Not sure what everyone has seen with PWC motors. My 94 XP runs a hair rich on the mag side with everything set equal and in good shape.

On all my rotax sleds I run staggered main jets wih one size difference between the two.

Make sure the carbs are clean with everything in good condition, needles and seats not leaking. If it runs good I wouldn't worry about it, but depending on the exact model there is more knowledge on this site than I have that might have more of an answer.

 

[Pwnage1337]

96 XP. I rebuilt both carbs they have less than 2 hours on them. I use genuine mikuni parts with brand new needle and seat. They both pop off at 34 psi, and the machine does 57 on the water. Runs great so I think I'm just going to leave it