Track Day Rider
Join Date: Nov 2009
Location: an undisclosd location
the tank on the zx10 is pressurised to push fuel into the manifold. your stock cap was designed to vent only after pressure dropped to a certain point after you turned it off. the vortex cap is a screw on, so when fuel splashes up to the trhreads, capillary action will hold it there, and when it gets unscrewed, the pressure pushes it the rest of the way. this is normal. carry a rag under your passenger seat to take the cap off with so it doesn't ruin your paint. it's the price you pay for pretty.