Leaky carbs

[Kool_Biker]

Ok, we are getting somewhere ...

But guys, the writing's on the wall. One of three:

1. My floats are of a wrong type
2. I set them wrongly
3. The brass pipes in the bowls are too short.

Oops, I think I have misled myself, and everyone else ...
I took the above measurements with the carbs placed vertical which is far from their operating angle ... which is quite a few degrees from vertical and places the top of the brass vent tubes COMFORTABLY ABOVE the fuel line. How silly of me to miss this.

So ... back to the drawing table.

Aris

[Kool_Biker]

I've seen this rear its head once or twice and, to give credit where it's due, I recall that Mike Nixon once made a very intuitive observation. What you may have there is, in essence, a distillery. Warm fuel, and more specifically the additives therein that have lower vapor pressures, will evaporate and condense in the cooler drain tubes.

My guess is that if you tried some aircraft gas you'd see the problem disappear; and also, that you are less likely to see this phenomenon in warm weather.

I've not seen it with my own eyes because I live in a year-round temperate climate, but that's all the more reason to attribute it to something other than float height or needle integrity (which are of course vitally important for their own reasons) as those variables do not change relative to climate. Try capturing the fluid in a glass vial for a closer inspection.

Hope this helps.

Jack

All above make sense to me Jack. Can you point me to Mike's write up (if there was one).

I HAVE captured the fluid, on several occasions, and it is consistently clear fuel with an oily residue, i.e. some clear oil (colorless, unlike engine oil) remains behind when the fuel evaporates.

Cheers, Aris

[Kool_Biker]

I've seen this rear its head once or twice and, to give credit where it's due, I recall that Mike Nixon once made a very intuitive observation. What you may have there is, in essence, a distillery. Warm fuel, and more specifically the additives therein that have lower vapor pressures, will evaporate and condense in the cooler drain tubes.

My guess is that if you tried some aircraft gas you'd see the problem disappear; and also, that you are less likely to see this phenomenon in warm weather.

I've not seen it with my own eyes because I live in a year-round temperate climate, but that's all the more reason to attribute it to something other than float height or needle integrity (which are of course vitally important for their own reasons) as those variables do not change relative to climate. Try capturing the fluid in a glass vial for a closer inspection.

Hope this helps.

Jack

All above make sense to me Jack. Can you point me to Mike's write up (if there was one).

I HAVE captured the fluid, on several occasions, and it is consistently clear fuel with an oily residue, i.e. some clear oil (colorless, unlike engine oil) remains behind when the fuel evaporates.

Cheers, Aris

Having just finished my 1K service, AND having repeatedly failed to find a concrete reason to explain my overflow pipe leaks (see earlier in this post), I now believe more than ever that it is indeed the Mike Nixon 'distillery' effect which is responsible.
To prove the point once and for all, I fired the engine in the garage, making it nice and hot and watching carefully throughout the overflow pipes. And indeed, almost immediately after the engine was turned off and began cooling down, condensation could clearly be seen, forming on the inner walls of the overflow tubes.

P1090886.jpg

Now WHY I get so much of it, is any body's guess. But at least I know my floats are otherwise OK and there are no needle leaks etc. Surely TBC, and of course suggestions always welcome.
Cheers, Aris

[Jeff Bennetts]

Aris, what if you put a TEE in the overflow tube about midway but before the hold down clamp in the pic you posted above to help vent the condensation, no extra tubing on the the TEE, just the nub of the tee pointing upwards.

Or a small catch can.

[CopperCollar]

I don't know about Greece but here we are mandated 10% ethanol and I have seen the stuff boil off when the engine is shut down.......

Mike

[Kool_Biker]

Both, good points chaps; I will research further.

And what comes out of the tubes IS a product of distillation; Yesterday, I carefully collected a couple of cc's to observe.
It is completely colourless (fuel isn't), runny like water, and if left to evaporate further, leaves behind a very flammable, colourless oily residue.

On top of all this, my carburation is near perfect, I KNOW my floats are where they should be, and this is only happening after a proper run, every proper run, when the bike gets nice and hot.

Cheers, Aris

[tevan]

Maybe you allready had this in your thread because I haven't followed it too closely but with the carbs on bike and bike on centerstand where is your float level with the clear tube check? Also I wander if this moisture is just comeing from one carb or a little from all. Just curious

[daves79x]

Aris:
I've not replied - waiting to see others' opinions. It's been long known that the CBX evaporates gas from the carbs like no other bike. Pull one into a small space after a good warm-up and the engine good and hot. Go back a while later and you will find a strong fuel smell - so strong that you will swear you have a leak. This is the reason primarily for the hard starting - there's no gas left in the bowls after a few days and what is there has gone very stale.

But to your 'problem', Aris - I think your floats are on the ragged edge of being too high. You will find that the fuel is nearly to the top of the standpipes when the bowls are full - not a problem until the fuel gets very hot from the hot engine. The combination of dense vapor and actual fuel expansion is dribbling some out the overflow tubes upon returning from a good warm-up ride. I've seen this a very few times and it's really not a problem if fuel does not pour out in normal operation. I generally set my floats a wee bit below the 15.5mm (I think that's what Honda calls for). By sight, with the tab just touching the pin without depressing it, I set all my floats to just BARELY above parallel in relation to the carb body. After what you've been through, Aris, I think you'll understand exactly what I'm talking about.

The check would be to pull #6 bowl and observe exactly where the standpipe sits ON THE BIKE, and it's exact height. Then reinstall the bowl and connect some clear tubing to the drain and fill the carb. Bend the tube around to the exact point you've marked the standpipe to be and see if you aren't right there with your fuel level.

In any case, right now it's not worth taking them off again to fine tune the floats - you've likely about worn out the things removing them as much as you have!

Dave

[Kool_Biker]

Dave

Let me start with reiterating that this is not a real problem. As YOU know, I have been to hell and back!
For once I seem to have a 'proper' CBX and I am enjoying every minute of it:
Always fires 1st try, has good compression, excellent cold / hot oil pressure, is oil tight & burns no oil, pulls like a horse, makes all the right magical noises* and in general, is a joy to ride.
So normally I wouldn't care about this; but you know how inquisitive I am; it is the intellectual challenge to get to the bottom of it as much as the nuisance of a few drops on the garage floor

I can relate with 100% with your post here, and I have done it all. However my floats are spot on 15.5 mm not a 'wee below' (I thought Honda float settings were religiously adhered to). And I wonder, as also observed by a good friend who PM'd me earlier, what would the overall effect be of running of the Z with say, 16.5 mm. As it seems the 'normal' 15.5 mm setting is quite rich, so how bad could 16.5 mm ever be? Food for thought.

In any case there is absolutely no way I am going to get them out again - it is not worth it for now.

*with the exception of a 'wee bit' more vibration than I would think 'normal' for a fully balanced six, over ~5.5K RPM - but this is another (intriguing) story.

Thanks a lot for your continued support
Aris

[EMS]

Aris:
. It's been long known that the CBX evaporates gas from the carbs like no other bike.
Dave

You have not had a Kawasaki KZ1300! It has been said that you can heat up a can of beans for your on the road picknick on top of the motor, right below the carbs.
This turns this bike into a notorious bad starter, especially right after it has been parked for a while following a ride. This is the reason why many owners add an electric fuel pump (I have done this) between petcock and carbs.

[ajs350]

Aris
I have this dripping issue on my 80. First it dripped out of both overflows but once I had removed the carbs for another cleaning (they really do take some effort!) and adjusted the floats again it only drips from the right side so I suspect the floats levels have some impact here. But like you I have not taken them off again as its just a couple of drips.
One other observation is that now that it has cooled down in NC it drips hardly at all so maybe the ambient temperature is a factor also.
Ross

[Kool_Biker]

I have this dripping issue on my 80.
Ross

Ross you mean in your 80 dripping occurs ONLY after a run, and it is a few drops on the floor like mine.
Aris

[ajs350]

Yes. It only drips after a run and it drips more when the ambient air temperature is in the high 80's and 90's.
It does not drip when cold and neither does it drip when I bench fill the carbs prior to installation.
As a side note my 79 does not drip at all....go figure!
Ross

[Kool_Biker]

Go figure indeed Ross.
And on top of all this, I wish I knew what sort of fuel we are served over here ..
Aris

[ajs350]

Try running it on some of that Ouzo I used to drink on the Greek islands when I was younger. I remember it had a high octane kick and I never dripped a drop. CBX compatible I'd say.
Ross