Honda BF50A carburetor diaphragm, confused!

[ErSa]

I have bought a Honda BF50A outboard 1998 BAZS-30000376. Then I took the carbretor from the motor it seems to lack parts around the diaphragm, se picture 1 and 3. There was no pipe #38 and no tubes #49? There is also no outputs on my carburetors as on a "normal" BF50 see picture 1 and 2. I have the diaphragm valve se picture 4. Question if I put the carburetors together, with a new pipe #38 where should I conect the three tubes to the pipe? New to 4-stroke / Erik

 

[MattFL]

What problem are you trying to solve? All that diaphragm thing does is hold the throttle slightly open for a few seconds when you chop the throttle, to prevent a stall when you pull back from lots-of-throttle to idle suddenly. If you're not having that problem then I wouldn't sweat it.

My 99' model year has it, but maybe your year didn't have it? The only other thing I could think of is maybe the previous owner replaced all 3 carburetors, but with carburetors from a different motor? Those plugs look factory installed so I doubt anyone removed the parts then plugged the holes.

 

[ErSa]

MattFL,

Thank for your answer. I just bought the motor and the the history for the motor was that did not run properly. It starts OK and the compression is OK (165 psi) so perhaps it is something wrong with the carburator installation.
Has to check the origin of carburetors and if they fit the motor. I reassemble and skip the diaphragm thing.
One curios question: Why is the diaphragm thing connected to the carburetors? Is there some under/over-pressure during deacceleration or ...? Erik

 

[flashback]

Vacuum increases when the throttle is chopped.

 

[Scott Danforth]

looking at the factory plugs in the carb, your carb came with the port closed off from the factory.

if you ever tried to get a drive-plug out, good luck, you would destroy the carb trying to get the drive plug out.

My guess, Honda realized the diaphragm is not needed.

 

[MattFL]

Start by cleaning the carburetors really really well. And then clean them again. Use an ultrasonic cleaner if you have one, and focus on the tiny pinholes that are near where the throttle plate closes on the carburetor and the circuits that feed them. Shoot cleaner and air through every hole, one of them connects directly to those pinholes. Be sure to remove the fuel screws and put cleaner and air through there too. If you've got the EPA screws, you might need to break the heads off to get them out, and you can replace them with regular fuel screws. The part numbers are posted around here somewhere, it's easy to do.

@Scott Danforth his 98' doesn't have it, but my 99' does, so I wonder if it was added in 99'?

 

[ErSa]

I have a clue, the BF 35A have a simpler "diaphragm thing" solution. The dashpot check valve is not connected to the carburetors. It is open, left to the atmospheric pressure. Next step is to find out if I bought a BF50A with BF35A
carburetors. I will be back....

 

[ErSa]

I have a clue, the BF 35A have a simpler "diaphragm thing" solution. The dashpot check valve is not connected to the carburetors. It is open, left to the atmospheric pressure. Next step is to find out if I bought a BF50A with BF35A
carburetors. I will be back....

It was BF30A carburetors on my BF50A. Has ta change 3 nozzels, $56.