Just as I was about to leave for the Shenandoah 500, I noticed a lot of liquid suddenly start coming out from the carbs and air filters. Not just a dripple, a steady stream of gasoline coming out the carb vent hose. It's never done anything like this before, I have no idea why it just started. The bike has sat for a couple weeks while I got new front brakes for it. Last time I rode it, everything worked great. Actually, everything still is great with the bike: starts easily, runs strong, etc. I just wouldn't get more than a few miles per tank at the rate it's leaking. I pulled the carbs off and checked the floats. Nothing seems to be sticking, everything looks clean and smooth. I adjusted the floats a tiny bit. I stuck the gas line in my mouth and blew into it. Plenty of flow with the carbs upright, but almost a perfect seal when I turned them upside down (as if the fuel level had raised the floats.) I had to blow a lot harder, but a little air would go to the bowls that way. Closed up the carbs again, checked that the situation was the same with the bowls closed, and same thing (though now the air flowed through the vent hose, obviously.) Gasoline still pours out. Repeated everything again, raised the floats a tiny bit more. No change at all. I really don't feel like I should have to adjust the floats at all, since it's never been a problem before, and they seem to be working correctly. I have no idea what else to do, though. Help? I was supposed to leave hours ago. It's a Ninja500 Parallel twin. I rejetted it several years ago when I changed the airbox to pod filters. Haven't had the carbs open since then. Never had any problems. I rode it about 200 miles a few weeks ago, and had no issues. Help?
i am experiencing exactly the same issue with my 125cc single gilera. i stripped and cleaned carb set float height and then set it up on bench and with fuel in it with a clear piece of fuel hose attached to the carb, filled with petrol and marked a line on the hose, i left it an hour and the fuel level did not drop, i then refitted to the bike and same problem reoccured. i am reasonably confident that the float needle and seat are good, my next job is to recheck the choke mechanism as the end of the choke plunger is 20 year old rubber i am hoping that this is letting fuel through even when closed. i dont know if you carb is simular please post if you find the cure
The springs on the float needles may be weak (happens over time), and between that and having the viton tips worn, may be letting fuel by with vibration from a running engine. On Connies, a trick to help with sealing is to put a little jeweler's rouge (or toothpaste) on a cotton swab and polish the brass seats for the float needles to make sure there are no nicks or stuck-on debris.
Are they leaking on the bench? Maybe pull a float bowl off, push the float up until the needle seats, then see where the fuel is leaking. Seems crazy that it could do that, but who knows?
I unfortunately don't have a bench where I am right now. I have a cul de sac outside my house where I'm doing this. I do know that if a vacuum is applied to the vacuum petcock, the same fuel flow will occur even without the engine running. So it's not vibration causing it. I'm not sure how to further test this. I suppose I could run the bike with the floats open, but without an auxiliary gas supply (without a vacuum petcock) it would be very tricky. I do have a bench in my workshop, but that's 200 miles away. Which is about 50 tankfulls of gas at this rate.
Do you have a Prime position on the petcock? That bypasses the vacuum control and just turns the gas on. I wasn't suggesting trying to run the bike without the bowls, just putting fuel to them to see if you can see where the fuel is coming from. I assumed that you were pulling the rack to work on them.
If your hoses do not have cracks in them pretty much the only thing left is the float- this is just leaking from one carburetor and not two, correct? and the needle valve. Look at the needle valve under a magnifying glass and inspect the seat for debris, and of course the proper and about only way to test foam floats is to weigh them. You might as well look for a broken O-ring somewhere but it sounds like a float or valve issue from what you describe.
...And since you do crazy shit you can get home by turning the gas on, then turn it off to start the bike and back on/off a few seconds at a time until you get on the highway then turn it on and slowly turn it off until it starts cutting out a bit then back open again until it runs OK. To keep from running too lean and burning a valve I'd open it a tiny bit more, not much just a hair. I wasn't going to post that and then I realized who was asking the question.
Sounds like a stuck float. Or crap in the needle valve. my ninja 500 did that after it sat for a couple of weeks. I not even months because the fuel gummed up in there. I
that's it. you say "bike sat for a few weeks" welcome to the wonderful world of ethanol. gums up very very quickly.
Is there an o-ring on the seat where it installs into the carb body? could be torn and letting fuel bypass the needle .
Got it. There was a little sliver of rubber or something caught in one of the float valves. All better now. May have come from the pod filter.
I had the same thing happen a month or so back. The tip on the needle was rock hard from ethanol exposure. I installed a new needle and was back in business.
That would be a neat trick, getting debris from the air filter into the fuel line. It could, however, be part of the inside lining of your fuel line. It may be time to replace it.
You may think it was because there was something stuck on the float valve mating service, but it was actually because whatever engine oil you use is the wrong one.
Make sure you do not have floats full of fuel. It is no at all unheard for brass to crack, seems Chinese brass may be brittle. Plastic and foam floats commonly leak.. Rod
What year EX500? We had this issue on my kids and replacement float needles fixed it right up (hoses and petcock were all good I have a carb rebuild lit for the first gen you can have if it is older then a '93 & I can find it
also carry a fire extinguisher until you get it fixed, I had a new to me bike catch fire that way and I was very lucky to be able to put it out with my gloves before I lost it :eek1 some of the overflow gas was ignited by the alternator wires. FWIW in my case the PO had installed new floats and they were a bit too wide at the pivot, no more overflows after I filed them a bit
