Kris,
the last K&B I bought new many years ago had a 13mm crank.
The motor should run on 10%, but will go much harder on higher nitro, at least 30%.
For the 10% you may need a fairly hot plug, try an OS 8.
What does the instructions say about a needle setting. I cant remember what I used on mine, but most engines I start about 2 1/2 turn and go in. the K&B needle might be different tho.
Ian.