Knowing some common issues, I just pulled it all apart to see if they may be the culprits. 1st thing I checked was the vent and then the drain. It vents perfectly when enough pressure builds up and the drain works fine. (I poured some fuel down just to be sure and it popped right out where it should behind the swingarm pivot bolt, I then blew it out with the air comp to make triply sure!!!) So it's neither of those I wouldn't think.
I checked the condition of the rubber, as the bike had sat for two years I figured it might be perished. But no, it doesn't have a crack, split or perish mark anywhere and actually is in better nick than the one on my ZX9, which doesn't leak. While there I had a good look. It appeared as thought the springs which force the rubber seal down onto the top lip of the filler hole, had lost spring tension. So, in the absence of a replacement part on Easter Monday, I pulled the cap apart, removed the springs and elongated them using the highly technically advanced needle nose pliers!!!!
I stretched them out about 30% more than they were and refitted the cap to the tank. It closes still, if firmly. So we will see on the next ride if that has solved the issue??? Anyone else had spring tension issues on Kawasaki caps???
