Clicking is a sign of a valve out of adjustment. My OS manuals say to adjust the valves after the first hour of running. I do it after the engine comes off the test stand, 2 tanks of fuel for break in. I then check them again after an hour, and then another hour after that. I'll give you a hint for keeping track of when to do you maintenance. I use a flight logging program to keep track of all my RC equipment. Get Flight Log from Shawn Lammers, www.lammers.ca. Set up and log all of your time with each engine. After every flight session log the flights and then print out an overdue maintenance report and it will tell you if it's time to check your valves, or any other maintenance you've set up.

On a side note, this program is a good reality check of how much time you spent flying, I'm talking about actual time in the air and not time spent at the field. So far for 2005 I have just a hair over 6 hours in the air!!!

Hope this helps.