I have a cateye fs509. I bought it used. On the bike, there is a sticker that says to run an oil mixture of 25:1. I run 25:1 through the bike, and oil leaks out the exhaust pipe. A fairly large amount of oil has trickled out. My friend that I bought it from also ran one tank of 50:1 mixture through it, and it also leaked with that mixture. Am I running too much oil in this bike? What is the proper mixture for the cateye fs509?