F40TLR Problems Running

[99yam40]

I got out of the mechanic business back in 78 so I missed out on the VV carbs. became an industrial electrician.

but i did get to play with a lot of q-jets

[rodbolt17]

in the above pictured diaphragm assy that is NOT a vacuum nipple.
it is part of the accelerator assy.

[99yam40]

in the above pictured diaphragm assy that is NOT a vacuum nipple.
it is part of the accelerator assy.

Does the linkage push on the diaphragm sending a pulse of air or fuel maybe?

[rodbolt17]

on some Yamaha 4 strokes the accelerator system uses a pressure change on the fuel bowl to force extra fuel up the emulsion tube.
remember a carb simply uses that 14+ mile high colum of air to move fuel.
it is entirely dependant on air pressure differential.

[99yam40]

interesting.
that would mean a restiction of the bowl vent is needed so the diaphragm could increase the pressure in there for a short time under acceleration.

[rodbolt17]

yep
and it is there.
most Yamaha carbs use a jet or an orifice to vent the bowl.
merc coined the term "back drag".
some of the multi carbed 4 stroke yamaha's use an accereator pump that simply pushs air into the bowl and the increase in bowl pressure makes the mixture richer out of the emulsion tube.
the old F40 is not one of these and it uses an actual plunger with some check valves to move fuel and squit it out a nozzle.

[99yam40]

Thanks for the info Rodbolt.

Do you plan on staying in the states when you finally retire from the everyday grind?

[pstephens46]

Rodbolt is not quitting. He will freelance at the fish house.

This stuff is in his blood.

Just like the rest of you...

[99yam40]

once you decide it is time to give it up, you do not want to keep on doing it.
I turned down many offers to go back and do some jobs.

Told them when I cannot make it on what I have coming in from retirement I will work for money again.
has not happened In 11 years and I dropped my master electricians license this year, because I do not believe I will end up needing it

[howardrya]

The boat is going back to the mechanic, we think the accelerator pumps aren't functioning correctly.