I have mnay magnums , this is what I learned .
1) as suggested get a great 4 stroke plug - the best
2) Pre-oil , pre oil -pre oil , I cant stress how much magnums needs oil, before , during and after , the workmanship is not as smooth on magnums as others so oil really helps .
3)make sure during the breakin period you allow the battery to stay connected undeer low idea, magnums need more breakin time . While most say three or 4 tanks , My first one was a 52 , it took 6 tanks and that baby runs like a $1000 engine now , but until the 5 or 6 it was a pain in the [:@]because I kepy trying to fly it after the second and third run .

I know its hard to be patient but , get 5 to 6 tanks thru these engine and you will be very very happy .There a great savings in money and have very good power