I just stumbled across these YouTube videos by poopdogsays on "Large Scale RC Carb Tuning" These are among the best videos I've found on tuning a Redcat Rampage or any other large scale RC...thanks to poopdogsays for creating these great videos.
Large Scale Carb Tuning Part 1
Large Scale Carb Tuning Part 2
How to Check for Spark in Your Large Scale RC
Be sure to check out poopdogsays' YouTube Channel for more great RC vids.