I have a 1978 JC Penney Swinger 2 and can not get the petcock to stop leaking. Just purchased the modped and it runs like a top. Bad news is the petcock leaks a lot in any position. Removed petcock, cleaned and inspected. No rubber seals just a plastic washer with grooves that are seated by the spring. The first thing I would like to do is replace the petcock. Not comfortable with buying something on-line that looks like it may or may-not work. The petcock base has threads along with the tank and a nut that secures both. Any suggestions?