I agree with your comment about the pics you posted. I was remembering the Hawk, for one, and the 25 that powered the plane I learned to fly on. That engine's low speed adjustment was the fuel inlet nipple that you had to adjust after REMOVING the fuel line!
The engines you showed were/are much better looking than my (early) experience. Like I said, I wasn't looking to start a fight, I was just trying to be humorous.....