A low whistling sound has been coming out of the gas tank of my ninja 250 for a while now just sitting in the garage. Its a low whine that lasts a couple seconds, stops, and then happens again a few minutes later. I was told that this is due to a gas cap vent, and that as gas is used, the tank pulls in air and that if my vent is crap or broken it will continue to suck in air after the bike is off. However, I opened the cap and left it ajar for about half an hour, but once I lock it up again, the sound will keep happening. I'm really confused as to why this continues to happen, I'm not leaking any fuel. Similarly, the bike has been running weird- I made a post about this a few months ago, but never was able to figure it out. The bike has been idling very high and bogging while letting out the clutch. I thought this was a carb issue, but I completely replaced the carbs with carbs a forum member sent me that were working perfectly, and the issue continued to occur Is there any chance these issues are related? What else could be causing my bike to run so strangely? Why would the gas tank keep whistling after I relieve the pressure and open it up? Thanks for your input and advice, I really appreciate it.
Haven't tried that yet. Will do. But if that solves my problem... what does it even mean? How can I permanently fix it, I'd rather not ride around with an open gas cap
my ninja whistles and vents off like that as well.. for weeks after I park it in the trailer... its probably not related to your running issue..
Yeah, it appears to be very common on the 250 bikes. I think you're right, unrelated to the performance problem... which is kindof worse, because I have no idea what it could be if it isn't my carbs.
Are you running gas with ethanol in it? Ethanol tends to expand and cause it to whistle. For your running problem, is the bike all stock? What are the fuel screws set at?
Any kind of gasoline will give of vapor whether it has ethanol or not. Gas will continually give off vapor until there is nothing left but goo if left long enough. The vapor is actually what helps your engine start. The whistling happening to your bike is most likely normal.
Thanks everyone - I understand the whistling is normal now, I've seen it all over the 250 forums after a little more searching. However, my performance issue is still the unsolved mystery. I think I will check hoses, as @tophyr suggested... I really don't know what else it could be. I got a stock-jetted carb so theres no other explanation for having such strange idling issues. A better description of the problem below: Bike only dies on the gas occasionally when leaving first gear. You have to rev it high and slip the clutch when you let it out or else it will die. there are idling issues in which the bike will warm up at a rather high idle then will idle down to standard / "normal" idle around 1,000 but if you ride the bike it will be very sluggish and boggish between 1 and 6 thousand rpm and then it will start pulling when its supposed to. you can stop the bike and it will idle at 1000rpm and if you rev it it will hang at about 4k for an excessive period of time, like a couple minutes, not seconds. And to be clear, The idle isnt set high, its set to 800-1000 rpm it will randomly rev up and hold an idle of 3-4k for an extended period of time, and then it goes back down. its really inconsistent. I've cleaned the carbs and swapped them out with perfectly good ones.
Two things to test are; Have you tried riding the bike for a few minutes, then opening the gas cap to see if it whistles any at all while open? Second, try, carefully, riding it around the block with the cap not closed completely to see if the high idle and bogging stops. It certainly sounds like a malfunction of the gas cap causing a lean condition by not allowing air into the tank fast enough while riding. (That would cause a restriction in the fuel flow out of the tank created by a vacuum.) Might be worth trying. Good luck.
Problem 1) there are YouTube videos on how to pull the gas cap apart and drill out the vent holes. It does solve the problem. If you can't do it, send it to me and I will drill it for you. Takes 10 minutes. Problem 2) the ninja carbs have very small orifices. We always ran Red line fuel injector cleaner thru the carbs after a weekend of racing. It does make a big difference in the low end idle of the bike. Good luck
it does sound like it's running lean, like orvis said. But since this whistling seems to be a normal-ish thing on that bike, I would be more inclined to check all of the rubber boots and what not that the carb is connected to. If there is a crack in those, you will get air sucked in thru them causing it to run lean as well. good luck!
Its pressure building up in the gas tank. The gas cap vent hole are clogged. Just buy an aftermarket cap (like the vortex v3) with a good vent system. Or you can be ghetto and drill it.
