I would like to know how to remove the filler cap from my 81 xj750,or more importantly,how to replace it once removed.when i turn the bolt on the outside of the tank it just spins the nut on the inside & whith the filler neck being a good inch & a half deep it means reaching down into the tank then back up onto the nut, i have not yet been able to figure out how to hold the nut still