For any EX 500 guru's, I've got a question for you. I'm helping someone get an EX 500 together that has been sitting for a while. We've done some simple maintenance, oil, brakes, etc. and I took it out for a test run last night. For some strange reason, when the fuel tank petcock is set to "ON" or "RES", fuel starts dumpiing out like crazy from the tubes at the bottom of the bike, but only when it's running. Even stranger, it doesn't do this when on "OFF". To get it home, I had the petcock on "OFF" then switched it to "ON" for a short time to get some more fuel flowing then back again. Everything seems to be hooked up alright and we've cleaned the carbs. Any info or ideas would be helpful. Thanks! P.S. I am not, nor do I profess to be a mechanic!
The petcock if vacuum activated so the gas only flows when their is engine vacuum. I would say you have a stuck fuel float that is letting gas into a crab until it overflows. When the bike is not running the petcock is turned off by the vacuum even if its in the on position. Good luck
Agreed. You can take the end of a screw driver and tap on the float bowl and maybe free up the float -or- Take the carbs off, open up the float bowls and clean out all the gunk that is in there. Get a can of carb cleaner and spray out all the jets, passages and (most importantly) the float valve seats. Spray down the fuel inlet while you are at it too. Check that the floats are not hanging up on anything and move freely. You can bench check that the float valve is holding by turning the carbs upside down on the bench (so gravity closes the float valve) and putting 1-2 lbs of compressed air to the carb fuel inlet. The valve should hold the pressure, and then release when you move the float. Put the bowls back on, put on the bike and see what it does. Don
Thanks, Don. I'll give it another look. We had actually opened the float bowls and got into the carbs to see how things looked and to spray some cleaner in anyway. This bike didn't even have an air filter on it, so I was expecting to find a birds nest or something in it. I thought the float bowls may have something to do with it, wanted a second opinion first. Think I may have possibly bound one or both of them up reassembling and reinstalling the carbs?
You have a stuck valve for sure. While you are cleaning that though, make your life easier later. Clean ALL the jets, but make especially sure to clean the idle jet (the small one inside a tube next to the mains). It has tiny holes, will not clean with spray carb cleaner and is probably the #1 EX carb problem (especially if the bike's been sitting). You may have to soak them in cleaner and use a piece of safety wire to totally clean them out.
Just to give you guys an update. I've re-cleaned the carbs on the EX, doing it a little more thoroughly this time. As before, the float valves appeared to be in good shape and there were no snags when moving them back and forth. I reassembled everything and cranked it up for a run. Surprisingly, it dumped fuel again until I tapped on the bowls of the carbs with a screwdriver handle while it was running. In short order, the fuel dumping stopped. The bike has run fine for a couple of days now. Thanks for all the suggestions/help guys!!
