I have a 1989 gl1500 and I am leaking a little gas from the petcock assembly. I just purchased the bike and i am replacing the diaphram inside the assembly first before replacing the whole unit. there is a small pinhole on the back portion of the assembly. does that pinhole go in on the top or on the bottom? there was so much grease and muck on thepetcock that i never noticed the pinhole until i cleaned everything up and went to reinstall the petcock. any help will be appreciated.