Fuel coming out of air box - Diagnosis

[mschor]

Mine occasionally leaks fuel to the airbox when I open the petcocks before startup.....but never while the bike is running. A light tap on the bowl always stops it. So what happens is the fuel in the bowl evaporates while the bike is sitting, dropping the floats to the bottom of their travel, then when you open the petcocks the bowls fill but the foat or needle gets stuck on its way up? Just visualizing why this only happens when the bike is sitting for a couple days, but never when its running or after a short pitstop. I was beginning to think there were elves hiding in there that would only come out after a couple days of quiet!

[Bonz]

The bike sitting for just a few days should not lower the bowl levels appreciably, IMO. Based on tapping the float bowl and the problem ceasing, a needle tip isn't sealing correctly or if you are parking on the side stand, the float is cocking ever so slightly sideways and causing the needle tip to not seat for one reason or the other like you said.

In the same vein your needle tips could simply be worn out and tapping seats them just enough.

[mschor]

I've also tried this before: Open petcocks, notice gas pouring out the airbox once the bowls are full, tapped the bowls til the leak stopped.....and then didnt start or move the bike, just shut off the petcocks and left it. Sure enough, the next time I came out and opened up the petcocks, once the bowls were full it started leaking again. I thought maybe it was some vacuum craziness, but theres no octopus

[Bonz]

If you have no octopus, you have bad sealing needle tips based on what you describe. The reality is the bowls should never be full. Full bowls are what spew out the airbox. They should get to a certain level and remain there if the needle is shutting off fuel flow correctly or if the needle seat O-rings are doing their job.

Try this before replacing the float needles.... Get some "3M General Purpose Adhesive Cleaner" on a terrycloth and gently clean the rubber needle tips. Put the 3M stuff on the cloth and spin the needle tips back and forth. Do it gently, you are simply trying to remove the gunk that has accumulated at the ring where the needle tip seats. A guru on the ZRX forum recommends this, works for me on keeping the same float needles in service and leak free.

Replace the needle seat o-rings while you are in there. Also, make sure there isn't any interference from the float bowl gasket inside the bowl where a gasket edge could be catching on the float and keeping it from shutting.

Link to cleaner, can also find at auto parts stores. https://www.amazon.com/3M-General-Pu...hesive+remover

[mschor]

Thanks Bonz, the needles are new but it could be in there or the floats. I was just commenting on it because it seemed such a curious thing that I could tap the bowls and fix the leak and then not touch a thing til next time I opened the lines and sure enough it was leaking full steam again. Seemed to defy logic, but I'm pretty sure I get how its happening.

[motoman]

+1 replacing needle-seat O-rings......if you haven't yet. Those needle seats CAN be difficult to pull out, but rocking them a bit while pulling up at same time helps release those internal o-rings.

[Thierry]

Update.

The bike running just fine didn't last very long.. Unfortunately I had fuel in airbox again.

So I went and read even more topics on xs11.com and then checked the carbs again. I discovered 2 things:

1) the carbs vents were pretty dirty. Air still could go through but, probably not ideal. So gave that a good clean.

2) I think I found the source of the leakage. One of the post that supports the float pin is broken at the tip. I never worried about that because the pin was still held correctly... But what I didn't notice is that the float tab is supposed to sit on that post tip to prevent the float to drop too far down in the bowl.
When the float drops too far, it allows the valve to stick out of the seat too much and gets misaligned. Then it won't go back in the seat even if the float pushes the valve upward due to misslignment.

I think I have a solution and would like to hear from you guys about that.
I have spare carbs. They're in bad condition and wouldn't use them as replacements. I was thinking cutting the tip of the broken post in my functional carb and Do the same in the spare. Then glue the good tip with JBweld to my carb.

Just unsure if JBweld will survive in fuel.. What do you think? Any better stuff to use? Other ideas?

Cheers

[motoman]

JB weld will NOT survive in fuel...it's already been tried, to no avail.

Someone here may direct you to the thread showing how to repair broken post.
I seem to remember something associated with using a drill press to hold carb stationary and drilling a small hole in remainder of post and in broken off section, then attaching both back in place using a tiny diameter short piece of rod.....or something to that effect.

[Thierry]

I've seen a thread about that. I thought that the suggested fix was tricky and requires equipment that I don't have..

I was thinking drilling (hand drill) and tapping both parts of the post and connect them using a small threaded rod. Easier done and needs less equipment..

I'm a bit surprised about the JBweld not doing the job.. They do a stuff for fuel tank repairs, thought that would work.

Also in one of my spare carbs, one of the post has been fixed with some kind of putty.. No idea how long it's been there. May never has been in fuel or may has been for ages...

[TopCatGr58]

Hey Theirry,

Do you mean this stuff?



Just googled it and found on Amazon. Hadn't actually heard of this, just the regular J-B Weld stuff. Note the description on the pacakge...fuel/ethanol
"resistant", not PROOF!? The float post will be submerged in fuel/ethanol 24/7/365.

We just know that regular J-B Weld won't work, but this stuff might?

You might do an experiment, mix a little bit, let it cure and dunk it in some ethanol fuel for a week and then see how it looks/feels?? If it's still firm, then would probably be okay....YMMV!

T.C.

[Thierry]

Yes that's ghe stuff I was thinking.

I googled it and some people said they fixed fuel tanks years ago and was still holding.

I might take the long/expensive/safe road... Take one of those spare carb body, give them a good clean and then send the carbs to the mechanic shop to get them swapped. I don't feel comfortable doing that myself. Especially that the motorcycling season is quite short over here.. don't want to miss a month of it because I messed my carbs!

[Thierry]

Just had an new idea.

What if I solder a tab on the float that would sit against the other post (which is unbroken).

Not sure what the material of the float is? Would a solder work? The kind of solder that we use to bond electric wires together?

[3Phase]

Just had an new idea.

What if I solder a tab on the float that would sit against the other post (which is unbroken).

Not sure what the material of the float is? Would a solder work? The kind of solder that we use to bond electric wires together?

Yes, you can solder a tab to the float support arm.

Be careful and clamp a heat sink to the support arms next to both floats so the solder doesn't melt and the floats don't fall off. It is not fun putting the assembly back together without a jig if you mess up and apply a little too much heat.

[Thierry]

For those interested, I did the solder fix and it worked perfectly.

I used a leg from an electronic component to make the tab, and just soldered it in the right position so the float rests at the same height as the others.

Little trick I used: I drilled a tiny hole in the float support arm, right where I soldered the tab. The solder goes through the hole and I used a drop of solder on the opposite surface. Way stronger than just "bonding" on one surface.

[dolphans1]

could be the octopus vacuum hoses are plugged up.