I have run the 35cc-RA and it is a great engine. i haven't done anything to it and it runs great. I haven't even changed the low or high adjustment. May need to make some minor adjustments as it gets more time on it. I am waiting for the plane to mount the 55cc-RA on. Will startbench running it to start the break-in while I am waiting for the airplane which is the Areoworks 55cc Yak 55M.