[amc49]

What are you saying 'whew'! for, he still has not fully traced out those passages yet and the answer still unknown.

Pic post #38, what is the passage ending around 7:00 in the pic? Where are the passages going to under the big rubber diaphragm? I don't see the twin idle air bleeds so the system has to add fuel rather than air and not clear at what point it does it with passages not fully traced.

Post #37......
'To test if Air cut of valve is sucking air from this passage i blocked it with finger and engine gradually died...'

The problem being if that is the idle air bleed you will kill it anyway and not tied to air cut at all. Did you ever put the spring back on top of that diaphragm if still using the whole rubber and steel center? If not a fuel leak there likely.

OP is getting lost in the details. If I had carb in hand it would be figured out in two minutes.

 

[SemiFast]

Most (probably all) of those air cut off valves do not cut off ALL of the air going to the pilot circuit.
My .02 cents worth of what ever this is.

S F

 

[amc49]

You are absolutely right if the valve is the sliding brass poppet thing, it has to have clearance to be able to slide effortlessly and that means likely at least a .003" leak to make sure of no drag at all there. That amount will leak. There are other poppet types that are spring loaded with a valve and those will not leak at all. The difference in a cheap 750 DOHC and an 1100 same, the two types are used, likely because the bigger cylinder has more vacuum on decel to leak.

 

[-Nate]

I'm saying 'whew' because I went through a similar thing with my CB125S, most would have junked the bike (in America it's a worthless oddity) but I like Mechanical puzzles and kept after it and now have a fine running / riding bike and he will too once he finds the little thing wrong .

 

[amc49]

OP still never tried both lowering slide (idle speed) and turning idle mixture shut at same time.

 

[SemiFast]

You are absolutely right if the valve is the sliding brass poppet thing, it has to have clearance to be able to slide effortlessly and that means likely at least a .003" leak to make sure of no drag at all there. That amount will leak. There are other poppet types that are spring loaded with a valve and those will not leak at all. The difference in a cheap 750 DOHC and an 1100 same, the two types are used, likely because the bigger cylinder has more vacuum on decel to leak.

In the carburetors I've been I believe I remember the pilot circuit having two air passages (ports) that work in conjunction with the air cutoff vale. Under high vacuum the air is cut off from one of those ports, not both, creating a richer mixture. I'm not looking at a carb as I type this so my memory might not be correct on that point... Just by memory so you know, not always exact.

S F

 

[-Nate]

Don't forget that the idle circuit and adjustments can be for fuel or air bleed ~ it depends on which side of the slide the mixture screw is...

If the screw is on the engine side of the slide it's a fuel screw .

If it's on the air intake side of the slide it's an air bleed screw and turning it in makes the idle mixture richer .

 

[amc49]

Yes to both the last two posts.

Need to know where the other two bleeds in post #37 pics 4 and 5 go, the ones OP has ignored. One will likely be main air bleed to main jet. If the other goes to the idle passage again, it will likely be the second idle air jet as mentioned in post #46. The idle airs will both join at the aircut poppet valve per #46 or the other will go into another fuel channel missed so far.

All this is moot and will have driven off most by now, the type that think they know carbs but don't. As well I have proposed more than one thing now to do and OP will not do them and still wondering why carb is acting up.

 

[UserXXX]

After last carb cleaning. The plug came out perfect. So the problem is solved though the mixture screw is only 1 turn out. Fuel mixture screw.

 

[-Nate]

Glad you stuck with it, now, GO RIDE ! .