This is the only engine i have with problems. I'm gonna add shims tomorrow and seal the backplate. Never had to seal an engine before. All the o rings look great. This engine has a break-in and 1 day of racing in my friends buggy and hasn't functioned properly since. And come to think abt it that's when i went from .020" shims to .012" shims because somebody else that raced one told me the RB manual said .012"(.3mm) was the proper shimming. OS is so much easier, lol.