I thought i'd post my impression of the zenon r on here. I broke it in with a new break in process posted on th rb forum. I changed the carb to one i had from a 35 plus21 i blew up and this engine is by far the fastest i've ever ran. I was running a 2018 pipe with a # 6 plug. 30% fuel with an extra .1 mm shim. I love rb engines!