Fuel pours out of carburetor overflow

[andthennugs]

Background:
'08 Ninja 250.
I have been working on the bike for a while and had the carb and gas tank off until recently. I've just put it all back together after cleaning the carb, thinking everything was hooked up properly.

Issue:
When I hold in the starter, gas flows (and I mean it pours) out of the carb overflow. I have double and triple checked to make sure the hose is in the right place.

2nd Issue: The tank is leaking out of the petcock (the hose where you can adjust from ON to PRIME) even when it's in the ON position. I have a feeling this is why the carb is so full of gas and is spraying it out of the overflow. It leaks a drip every 2-3 seconds and I'm currently draining the tank to remove the petcock and check it out. This was not happening a day or so ago (the only thing I've done is drain the tank, including removing and replacing the petcock but it was very easy to take apart and put back together, just two screws).

Troubleshooting completed:
Percussive maintenance on the carbs.
Replaced spark plugs (needed to be done).
Double-checked hoses to make sure they were routed properly.
Took the tops off the carbs to make sure they were set up properly (and watched a video of someone taking them apart to make sure).
Downloaded a manual which has NO information in it regarding carbs from Kawasaki's website (https://www.kawasaki.com/ServiceManuals/Manual/EX250J8F)


Hope I didn't forget anything.

[InvisiBill]

If your carbs are overflowing, you inherently have a problem with your float valves. They close when the carbs are full, stopping any more gas from coming in. If gas continues to come in, it means the float valves aren't working.

If you have gas coming out of the petcock without engine vacuum, the petcock also has issues that need to be addressed. If the rubber in it is bad, you may also be sucking fuel in via the vacuum line. If it gets much worse when you're turning the engine over, it sounds like the vacuum operation of the petcock is still at least partially working though.

Also be aware that excess gas from the carbs can run down into the cylinders, then into the crankcase. Check your oil and change it if needed.

[Triple Jim]

Another danger is fuel in the combustion chamber causing hydrolock when you try to turn the engine.

[Demonik]

Most definitely, the floats are stuck in the down position, that is the overflow tube venting the excess overboard.

I had a rescue project bike this spring that had this same thing happen. It sucked so much fuel from the carbs just inhaling raw fuel that the cylinders packed with gas and the oil had fuel in it too.

What I ended up having to do was change the oil (it gets thinned by the gas and ruins your oil) and filter, empty out the airbox (it had gas in there too) and change the air filter (fuel ganked that up pretty well too).

"percussive" maintenance on the bowls, or hammering them, won't help a stuck float on an old bike. The carbs HAVE to come off, the bowls HAVE to come off, be cleaned, the jets HAVE to come out and be cleaned, they need to be spotless. You can't just soak them and replace them. You'll need to spend a few minutes boiling the jets (slow and main), needles, and whatever else that isn't plastic in water for 5-8 minutes to loosen it up and then using a wire tie stripped down carefully to get the "verdigris" or copper carbonate off the brass.

[joehendo]

I have the same issue - could use some help. My carburetors starting dripping at the track day last month, just out of the blue. Didn't pass inspection of course, so it sat all weekend. We thought it could have been the float valves, so tore them down for inspection, but they were working fine.
I ordered all new float valve carb kits the following week, installed new kits, cleaned everything up and still dripping like crazy. I took the carbs off again and did a more thorough inspection - took out all the jets and noticed the pilots were dirty (should have done that the first time). Replaced those with a set of brand new ones that I had. All the rest were good, but I went through everything with carb cleaner anyway. Buttoned up everything and still the same results...overflowing gas again...argh!
No gas flows when petcock is in ON position unless bike is running, otherwise not sure if I have a petcock problem?

Any thoughts appreciated.

[DannoXYZ]

So carbs only overflows when bike's running?

Did you measure float height?

[Triple Jim]

It shouldn't leak when the engine is not running if the vacuum petcock is working correctly (pregen I assume). That leaves leaking float valves, float height too high as Jean Philippe was suggesting, or a cracked overflow tube if these carbs have them (I can't remember).

[ducatiman]

Originally Posted by joehendo

I have the same issue - could use some help. My carburetors starting dripping at the track day last month, just out of the blue. Didn't pass inspection of course, so it sat all weekend. We thought it could have been the float valves, so tore them down for inspection, but they were working fine.
I ordered all new float valve carb kits the following week, installed new kits, cleaned everything up and still dripping like crazy. I took the carbs off again and did a more thorough inspection - took out all the jets and noticed the pilots were dirty (should have done that the first time). Replaced those with a set of brand new ones that I had. All the rest were good, but I went through everything with carb cleaner anyway. Buttoned up everything and still the same results...overflowing gas again...argh!
No gas flows when petcock is in ON position unless bike is running, otherwise not sure if I have a petcock problem?

Any thoughts appreciated.

In order to know more....precisely WHERE were they dripping from?

If vent tube, that would indicate a runaway float valve issue as the vent is WAY above correct working fuel level.

If some other source...???? Dunno...gotta be more specific.

A bench wet test would reveal. If needed, I stand at the ready.

[joehendo]

Sorry, should have mentioned, bike is a 2009.
Carbs don't leak when the bike is not running.
When I fire it up, the gas looks like its dripping from the left and right screws holding the lower bracket on...doesn't make sense!

[joehendo]

I have not measured or checked float height - is there a thread on how to do that? Thanks.

[DannoXYZ]

Here's a good one: https://www.ninjette.org/forums/showthread.php?t=279385

[joehendo]

Good deal- thanks. I will check the levels!