Which jet is idle and which is high speed on the carb?

[JohnWI]

I'm doing the search function AND looking at the parts diagrams for my motor, but they only say "orifice #..." so I'm asking here.

1984 Ev 70HP triple which seemed to be dry on my top cylinder during idle. I pulled it off, gas was in the float bowl and seems pretty clean, overall. Not to say that a small air leak couldn't exist. I do have my rebuild kit. The smaller fuel inlet was clean and I could see through it.

I was hoping that either YouTube or here would have a sticky that shows a diagram of which jets are which? I understand I need to take out an outer screw to reveal the jets.

 

[JohnWI]

Re: Which jet is idle and which is high speed on the carb?

Compression is good on all three and I didn't test spark...but my thought re: spark is that if I didn't have spark, my plug would have been very wet and dirty. Sound like a good assumption?

 

[Chris1956]

Re: Which jet is idle and which is high speed on the carb?

The parts diaghram shows 3 jets. The one in the base of the carb bowl is the main jet. The upper right one is idle and the third (upper left) may be an off-idle jet ro something else (mid-range jet?)

 

[JohnWI]

Re: Which jet is idle and which is high speed on the carb?

http://shop2.evinrude.com/Index.aspx?s1=o475g4gqfjrumml0fdst0ccmm5&catalog_id=0&siteid=1

Is the diagram (assuming the website doesn't muck it up).

For the 70 I was expecting to see a needle, but I only see that the 75HP model has it (#31 in diagram). I have pulled parts 22 and 27 and they looked fine. So does the float seat and needle.

Since I'm here and all looked good should I change the parts out or just reassemble only with new O rings and gaskets?

Now here's what I consider the bigger question:

Am I dreaming or did the PO forget to install one of the core plugs? Part#5 looks to be on the external body, but I can't quite tell if part #4 in the diagram is on the inside of the body as it does say two are required.

Any issues with that center tube not being truly centered in the jet housing? Please correct my incorrect naming of these parts.

Without a needle going in/out, I don't understand how you adjust them?

 

[daselbee]

Re: Which jet is idle and which is high speed on the carb?

No adjustment dude.
The center tube is supposed to be offset. The small tube is the idle fuel supply. Make absolutely sure that tube is clear. I use a long welder's tip cleaner to ream it out, if necessary.

Any adjustment (and there shouldn't be any needed) is done by changing jets. Tricky procedure to get it right.

EDIT: PArts 4 and 5 are all on the outside of the carb.

 

[JohnWI]

Re: Which jet is idle and which is high speed on the carb?

Thanks. I'll try and get something to try to run through it or blow through it.

So you don't think that the open hole in the upper part of my photo is (missing) a core plug? I wasn't sure it was, but with the carb kits coming with "extras" to supply more than just my model, it's hard to know.

I did see other plugs on the outside.

I'm guessing that small inner tube may have a blockage as the unit runs at speed, but not at idle and a bit rough at speeds just over idle.

 

[daselbee]

Re: Which jet is idle and which is high speed on the carb?

"So you don't think that the open hole in the upper part of my photo is (missing) a core plug?"

Hmmm....open hole in upper part of photo....you mean at the 11:00 position to the needle seat?

Nope. In just thinking on the carb theory, and the way they manufacture the castings....the core plugs are used to seal holes that they needed to make "on the other side of" the core plug.

They had to drill thru, or make some manufacturing detail, and then they sealed it with a core plug.

So, behind the core plugs, there is generally a very small passageway that needs to be absolutely clean. Small holes leading to the venturi....things like that.

All core plugs that I have seen are on the outside of the carb. I have not examined your particular model carb, but I have looked very very carefully at the 1980 V4 crossflow carbs. I think you have a blockage in the idle tube (offcenter tube) and it's following fuel path. You gotta study it, and see where that fuel flows from up from that tube. It will go into the carb body top...and then on to the side of the venturi...micro holes.....right at the throttle butterfly.

I had a V6 looper that wasn't running right at idle. Crappy. But I just did the carbs, and cleaned the idle side very very thoroughly.
Ran it....ran OK...but then detiorated. Soon wasn't idling right at all.
Absolutely guaranteed that it wasn't the carbs. After all, i just did them. So I thought.

Tore them off, and crap. All of the carbs were blocked in the idle circuit by ???? to this day I don't know what it was. It was grainy, almost like very, very fine sand. It was NOT sand; I have two filters on incoming fuel lines....water separator....etc.

I seriously regret this...I failed to taste the grainy crap. I would bet to this day that is was salt. On these carbs, there is an air path that could take in salt water, and after evaporation, leave the tube tops full of salt. Just a theory. Yours can't do that, I don't think. But....

Clean that idle tube, blow thru it with your mouth, suck thru it with your mouth....you can tell more about how much it is flowing by sucking on it....you can feel the air on your tongue....I tell you true.....

Tastes bad, but you will live.