I've a Mountfield with a B&S 11hp engine and a spare engine out of a Westwood. I'll take a look at them tomorrow if I get the chance. Though the Mountfield throttle/choke arrangement, now works the wrong way round. slow is fast and fast is choke and slow.
I had problems with it's running when I got it. Played about with the linkage, not really knowing what I was doing and it goes like stink now.