Leaky carbs

[Kool_Biker]

After every ride and upon my return, my Z will ALWAYS discharge a few cc's of unburned fuel onto the garage floor through the overflow tube.
It will never leak more, and it will NOT do this with the engine cold and the fuel tap in the 'on' position (no vacuum valve in my Z).

Do you think the state of the float valves (1 to 3 shown here, the others very similar) below, could explain this ???? They look good enough to me.
I have a new set but would like to know your opinion before I replace them.

P1090774.jpg

Please be aware of the magnification here.

Best, Aris

[bobber01]

Valves look good to me, assume the seats have no markings? And floats adjusted equal? If the carbs are totally disassembled may be a thought to bench re-assemble, hook up a fuel supply and you may be able to pinpoint exactly which carb is leaking and from where.
Any fuel in your air box? Few years ago one of my X's would dribble fuel from the air box drain tube. Turned out to be a combination of things was causing the carbs to 'spit' fuel into the air box.

[Jeff Bennetts]

If the fuel is coming from the overflow check your stand pipes in the bowls, they are prone to crack and this causes leaking through the overflow even though the float and needle are working correctly.

You can check them with compressed air.

[Kool_Biker]

If the fuel is coming from the overflow check your stand pipes in the bowls, they are prone to crack and this causes leaking through the overflow even though the float and needle are working correctly.

You can check them with compressed air.

I've just done this test, carefully, and all six stand pipes check negative when cold and on the bench.
I wonder if heat, say at ~ 80' C will make any difference, e.g. a hair line crack which shuts down when cold?
I did mention this only happens AFTER a ride and then stops ...

Frustrated ...

[Kool_Biker]

Valves look good to me, assume the seats have no markings? And floats adjusted equal? If the carbs are totally disassembled may be a thought to bench re-assemble, hook up a fuel supply and you may be able to pinpoint exactly which carb is leaking and from where.

Bobber, I've done all this ... When cold or wet tested on the bench the problem goes away ...

Aris

[NobleHops]

This is a post I probably ought to write and then delete, but I'll offer a theory. If the carbs aren't venting properly, then I imagine that back pressure from a warm bike could easily build up in the carb bodies after you stop. In which case the drains are working perfectly, stuff is just getting forced out due to higher internal pressure. And that could move around depending on which intake valves were open when you stopped I further imagine. How about checking the other end, eg the vent circuits instead of the drains?

N.

[Kool_Biker]

I am glad you did not delete the post Nils, but cannot BEGIN to understand where you are getting at!

P1090779.jpg

The overflow stand pipe orifice is sitting well clear of the fuel line in a correctly filled carb bowl.
The only way fuel can escape from there and into the overflow pipes (through which I get the fuel drops on the garage floor) is if, for some reason, the fuel level rises enough. Could the fuel from a hot bike be boiling in there, may be?

I can see no other way whatsoever. But may be there is something I am missing ...

Aris

[zxbob]

Did you ever remove the overflow hoses and try to determine if its coming from a single carb ~ or all six ?

Also FWIW the very slight ridge I see in the #2 needle "could" be enough to let pass (just IMHO)

Bob

[Kool_Biker]

There are 2 overflow pipes (3 carbs each - I have adopted the 1980 model system) and both leak ..
Cheers, Aris

[NobleHops]

I am glad you did not delete the post Nils, but cannot BEGIN to understand where you are getting at!

As I was saying...

Just thought it possible that if the carbs were not venting properly it could create problems with the levels. There's your short version. <relurk>

N.

[Jeff Bennetts]

Nils is saying the two carb vent tees, one for each set of three carbs may be blocked, not sure how it may effect the build up of pressure but it will hinder the carbs from flowing fuel.

Three other possibilities, the drain screws aren't seating(the tapered tips), incorrect float level or the stand pipes aren't seated in the bowls ?

[Kool_Biker]

Nils is saying the two carb vent tees, one for each set of three carbs may be blocked, not sure how it may effect the build up of pressure but it will hinder the carbs from flowing fuel.

I understood Nils's point all along. But like you, cannot see how this can be related to my specific problem.

After some thought and an exchange of helpful PMs with Don, I have decided to replace all 6 valves with brand new ones I bought off TIMS back in January. See how it goes

For your observations and thoughts, I attach a pic showing one of my existing 'old' needles (on the right) next to a brand new ones from TIMS (left).
Consistency wise (and this is my nails talking), the new needle tips are appreciably softer than my 'old' ones.

P1090787.jpg

Ah, it's all about the voyage of discovery.

Best, Aris

[Jeff Bennetts]

Re-check your float levels after you install the new needles. How do the plungers on the old needles feel, free with plenty of lineal resistance or collapsed and sticking ?

[Kool_Biker]

Old plungers: Totally free with plenty of linear resistance, not collapsed in any way and not sticking at all Jeff.
I have a feeling, the old ones are (still) better than the new ones, with the exception of the pliability of their rubber tips when pushed slightly with my nail.
Aris

[Kool_Biker]

After some thought and an exchange of helpful PMs with Don, I have decided to replace all 6 valves with brand new ones I bought off TIMS back in January. See how it goes

Ah, it's all about the voyage of discovery.

Best, Aris

*%$&@%*!!! and again, *%$&@%*!!!

Unfortunately, the new needle valves have different internal spring ratings, you can even tell by pressing with one's hand, an inconsistency which I know will create more problems than I am trying to solve in the first place.

So, I am back and stuck with my existing valves ... until I get a brand new set from Honda ...

So much for the 'voyage of discovery'