Posted July 14, 2014 Hi chaps.The yellow bike is almost finished,but I have a strange problem. Everytime that I run the bike ,wether for a few minutes or longer If I then open the fuel filler cap I get a big sucking noise and sometimes a bit of spray too. Before everyone jumps in I have done the following. Removed the tank and checked out both the tank breather and the fatter fuel overflow pipes by blowing down them once they are disconnected..they are fine,they are also not trapped,kinked or perished.I have then attached some clear hose to the outlets beneath the tank and blown through them and they are clear as well. I have also pushed a length of wire down these holes and found no obstructions.... I have found that blowing through a lenght of tubing attached to the thinner tank breather works o/k you can feel the air coming bthrough a small rubber block located about 5 oclock inside the fuel filler ,but as soon as the cap is in the locked position I can no longer blow through it.I have lifted the tank on my other X11 and done the same and I can still blow through the breather pipe when the fuel cap is closed... The problem is in the fuel cap area ..I am convinced. I Have lastly removed the fuel cap assembly and inspected it and all looks O/k?? Am i chasing nothing here??My Blue X11 doesnt have this problem... Would my bike ultimately stop working after a gallon or so is used as the tank vacuum increases to a point where it is too powerful for the fuel pump??Could it even lead to a physically damaged fuel tank??Could I potentially be unable to open the fuel cap after a long run beacuse of the vacuum created?? Does anyone elses bike do this??Does my bike do this because it has stood for many years? Does my bike do this because it is low mileage.. All suggestions and help appreciated. 0 Share this post Link to post
Posted July 14, 2014 It might be the fuel return splashing back into the tank? 0 Share this post Link to post
Posted July 15, 2014 I had this problem with mine, it never stopped the bike working, but I carry a mini screw driver round because the filler was stuck tight, in the hot weather it wouldnt budge, but I cleaned up the filler cover and blew compressed air all around it and now it doesnt stick that much. This weather will cause a bit of a vacum. 0 Share this post Link to post
Posted July 15, 2014 So are you still getting the sucking sound on opening the filler cap then Jason or has it disappeared?? 0 Share this post Link to post
Posted July 15, 2014 So are you still getting the sucking sound on opening the filler cap then Jason or has it disappeared?? No, the cap sticks a little but will open pulling on the key slightly, I cant remember if it was this site or somewhere else,but I was told to blow compressed air around the bottom of the filler as there is a little air hole, don't know how true it is but I did and whilst it didn't fix it totally I no longer have the embarrassment of a locking petrol cap when I fill. I used to have a car that would make a sucking noise when I opened the filler, it wasn't anything to worry about. If there was a lock you would lose power and stall pretty quickly anyway. 0 Share this post Link to post
Posted July 17, 2014 Have you swapped the fuel caps to se if the problem moves with the cap Andrew ? 0 Share this post Link to post
Posted July 18, 2014 I was thinking of that.Will give it a try on sunday John.The soaking in brake cleaner and then a blast with air compressor didnt do anything.It seems to be the cap crushing the rubber breather block when locked.Anyway..I was thinking of swapping the cap assembly as you suggested.Also I was going to brim the tank and do about 50 miles and then do a cap check. If it opens o/k..go a bit further,say 100 miles before checking to see if the cap gets vacuum locked. Will keep you posted 0 Share this post Link to post
Posted July 21, 2014 Well...The bike is now fully commissioned so to speak I brimmed the tank and went for a quick 50 mile run yesterday....it ran smooth and pulled hard,it ticked over and never missed a beat,Got home ,opened the cap, slight venting noise,the cap opened fine...So cant be much amiss. 0 Share this post Link to post
