My experience with the 61 is lack luster. It’s been difficult to tune for some reason and it’s flown one season. I’ve tested several props, increased cooling, made sure the reeds and block are dialed in, I use Klotz exclusively and Non-E gas, NGK plug, etc, but it’s just underwhelming. The 55RA would run circles around this engine and I’ve had a 55RA and 55 before this one. The 55 was in a TF Mustang and it ran excellent in that tight cowl. I ordered a Xoar 23x10 to try next and see if a little less load will help it. The compression feels weak to me so it will get a Bowman ring after I inspect the jug for scarring or any excessive wear.
So I ordered the 65 anyway last night after thinking about it and I figure DLE must have decided to phase out the 61 or why make a new engine so close in displacement. The extra claimed half horsepower at 7500rpm sounds good. I wish they would make all the new engines with rear exhaust!