New to jets, question regarding my carb 2015 Yamaha YFZ

[Je m'appele Claude]

I got a question regarding jetting because I'm quite new to this. All stock for the 2015 Yamaha YFZ carb version. I know that the main one is this nozzle kind of and has the value 155, but I'm not sure which one is the pilot jet and which one is the leak? Tiny one has 55 and one has 46.5 so which is which? How to dial it better suited for me?

 

[petest0pp]

So on your YFZ, the 155 is definitely the main jet, handles the top-end fueling.
The 46.5 is your pilot jet. It controls the fuel mixture when you're idle or at the low-end.
The 55 you mentioned is likely the leak jet, which affects the accelerator pump's squirt.
To dial it in, start by adjusting the pilot circuit for a smooth idle, then the main jet for good top-end power.
Then tweak the leak jet for crisp throttle response. You have to listen to the engine and see how it responds.
Hope everything's clear.

 

[onlyneatwhiskey]

I got a question regarding jetting because I'm quite new to this. All stock for the 2015 Yamaha YFZ carb version. I know that the main one is this nozzle kind of and has the value 155, but I'm not sure which one is the pilot jet and which one is the leak? Tiny one has 55 and one has 46.5 so which is which? How to dial it better suited for me?

On your YFZ, the 155 is your main jet, like you said, and that handles throttle wide open. The 46.5 is your pilot jet, which controls idle to low throttle response. That 55 is your leak jet, part of the accelerator pump circuit, it affects how quickly extra fuel gets pushed in when you stab the throttle.
For the rest, @petest0pp has taken the words right out my mouth

 

[JemP1990]

The 2015 probably has a Keihin carb, try a smaller 42 pilot jet instead of 47 and keep the main jet at 152. The 55 is likely a leak jet, so just leave it alone. Turn the fuel screw out about 1.5 to 2.5 turns. Also, check the needle... If it's not adjustable, you can get an NCVQ needle to help with its tuning.

 

[collincolt45]

Basics of jetting fuel delivery:

Pilot jet: idle to ~25% throttle

Needle: ~25% throttle to ~75% throttle

Main jet: ~75% to 100% throttle.

Hope this helps.