What does this orifice plug (carburetor) do?

[fmjnax]

On my carburetor, I found out that there are two orifice plugs on the bottom cover (in the bowl). One of them was partially clogged. I'm wondering what these orifice plugs are for and what sort of impact a partially clogged one might have.

The engine is an '84 Johnson 115 V4. The orifice plugs are #3 in this diagram:

 

[Joe Reeves]

The two jets in the bottom center portion of the float chamber are "High Speed" jets. They need to be perfectly clesn in order for the engine to obtain the proper amount of fuel for high speed operation. Also fuel needs to flow thu those jets before the fuel can flow to any other (idle/intermediate) fuel passageway... so you can see that their cleanliness is most important.

 

[fmjnax]

Thanks Joe!

Would it be possible, then, to get a lean sneeze at idle if one of them was blocked? Long story short, I've been investigating a lean sneeze at idle and haven't been able to fix it, even with a perfectly clean and free low speed orifice.

 

[Joe Reeves]

No, the high speed jets are not the cause of your sneezing problem. To pinpoint which side of which carburetor is the problem area... with the engine running and the sneezing condition taking place, insert two fingers into the carburetor throats. When you come to the offending carburetor, the engine should smooth out.

Now, the idle jets exist at an angle at the top inside front portion of the carburetor. Keep in mind that these are Idle "Air" Bleed jets. They DO NOT measure fuel, they measure air!............ Replace the offending idle air bleed jet with a smaller size one. The jets are clearly marked on theur face as to what size they are, go one size smaller at a time as you DO NOT want to create a rich condition to replace a lean condition.

Let us know how it goes for you.

 

[fmjnax]

Thanks again Joe. I've got some other threads on the subject of my carb adventures so I'll just keep this at a summary. I have replaced 3 of the 4 low speed orifice plugs and cleaned and soaked the carbs. The sneeze appears to be gone, but it was short-lived. Stupid me decided to use gasket compound on the float chamber gasket and it turns out that the gas dissolved it and plugged up the carbs to where the thing wouldn't even run. So I've stripped and soaked and cleaned the carbs yet again (this time without the gasket compound). This is when I noticed the partially blocked high speed jet (and ultimately my question about symptoms).

Lake time is Saturday, so we'll see if I got it all out and if the sneeze really is gone.

 

[F_R]

Joe contradicted himself. In post #2 he said that a plugged high speed jet also obstructs the idle passages. That is true. It would also cause the motor to run on three cylinders at high speed. However, I do agree that it probably isn't plugged to the point of more or less completely cutting off the idle fuel and making it sneeze. In any case, bottom line is everything needs to be clean.

 

[fmjnax]

Thanks F_R. How you worded it is how I interpreted it, so all good.

That one plug was only maybe 25-33% plugged. I could see light through it, but my feeler wire wouldn't go through like it would on the other 3. That has been corrected.

 

[Joe Reeves]

Joe contradicted himself. In post #2 he said that a plugged high speed jet also obstructs the idle passages. That is true. It would also cause the motor to run on three cylinders at high speed. However, I do agree that it probably isn't plugged to the point of more or less completely cutting off the idle fuel and making it sneeze. In any case, bottom line is everything needs to be clean.

I really hate that and wish you hadn't made that remark. That's not what I said in either reply and even if I did, if it's true, it's not a contradiction. What I said was "Also fuel needs to flow thu those jets before the fuel can flow to any other (idle/intermediate) fuel passageway... so you can see that their cleanliness is most important." Perhaps I should take up house painting!

 

[F_R]

Am I nuts or blind? You said "Also fuel needs to flow through those jets before the fuel can flow to any other (idle/intermediate) fuel passageway.." Isn't that the same as saying if it is obstructed it will also obstruct the idle passages?. Put away the paint brush, I'm agreeing with you.

The contradiction is in post #4 where you said obstructed high speed jets would not cause a lean sneeze. If gas can't get through the high speed jet, it can't get to the idle system and it might sneeze. But the high speed would have to be mighty well plugged for that to be the case......that's all I was suggesting.

 

[Joe Reeves]

F_R... I did not use the words "obstructed" or "plugged"... and the words that I did use are not interchangeable. Don't know if I'll take up house painting but I think it's best I leave the forum. Been here for over twelve years... time for another path.

 

[fireman57]

Don't run off yet Joe. If I can't figure out my problem tomorrow I will send you a pm.

 

[F_R]

Don't go, you are a valuable asset here. I promise not to reply to any of your posts in the future. Fair enough???

 

[Tim Frank]

C'mon guys...play nicely. You are both way too valuable to lose!
Heck, if there is only room for 2 in the lifeboat, you 2 guys get in it, I'll go down with the ship.

 

[clanton]

Joe, you can`t leave. Lots of folks seeking answers for these motors and you have them.

Clanton

 

[fireman57]

I know of no one who is so specific with technical advice as Joe. He has even CALLED me to help me work through a problem. When I follow his advice to the letter it solves the problem. FR you've been around for a long time too. I've noticed that there aren't many of us "old timers" left. It just seemed childish to me that not responding to any of Mr. Reeves posts would solve the problem to you. Why not work together and not call someone out just because you can.