Thought you might be interested in the following:-
Several years ago I was getting ready to replace one of my KB 61's which was getting a bit "doggy" after over 10 years of hard use when I discovered a new piston and ring (dykes) I had in my parts box from a Merco 61 fit the liner almost perfect! With a bit of enlarging and squaring of the bypass ports to line them up, and some dremel work on the head to clear the piston baffle, I soon had a KB/Merco 61 ready to run! And run it did - and extremely well! I flew it in my "Redbird" Bipe
( see http://www.quiknet.com/~pheller ) and it certainly outperformed the original KB, even when it was new! I mentioned it to C. Lee whose only comment was My original KB must have been a dog! Interesting since he designed the Veco 61 originally with a dykes ring!

Phil