05 Yamaha F40 accelerator pump drill out

[Bluesmoke]

2005 Yamaha F40 F40ELHD

This is a question that's been asked on this forum before with no clear answer:

Yamaha 40 four stroke with carbs, and the accelerator pump on one or more carbs is clogged, even after ultrasonic cleaning. Apparently there's a process and/or modification (rumoured to be a Yamaha technical service bulletin) where something somewhere on the carbs is drilled out to assist cleaning.

If anyone has firsthand knowledge and can confirm that this is a real thing, and better yet, can explain the process, please post it here and get this information out there.


*boscoe99, you PMed someone about this a while back about this topic, is there something you can share?

[boscoe99]

A clear answer was provided many many moons ago but it is now long gone.

When you refer to something being clogged are you referring to the nozzle in the carburetor inlet that spritz's fuel into the carburetor when the throttle is advanced quickly?

[boscoe99]

Oh, there is no Yamaha technical bulletin that specifically addresses the accelerator pump on the F40 model.

[Bluesmoke]

Thanks for the reply.

Turns out it was the pilot jets. They needed to be set at 2.5 turns out (or more) and the carbs balanced. I think these motors were delivered from the factory running lean (for emissions).