The 1250 with a 1/4" or 1/8" crank will give you a 1350 or 1300 respectively. The 1320 only has 2 ring pistons where has the 1250 has 3 ring pistons, plus the stroke will give you more torque :angeldev:
MAYBE YOU SHOULD TRY TO GET DYNO FIGURES ON BOTH 1250 AND 1320 SET UPS. i WOULD RECOMEND THE 1320 BECAUSE SIZE DOES MATTER! HOWEVER, EXPENSE IS ANOTHER ISSUE. MAYBE WE COULD GET HP COMPARISONS BETWEEN THE TWO. I'M SURE THERE ARE PEOPLE IN THIS FORUM WITH 1250'S AND 1320'S .?.?
I HAVEN'T HAD ANY PROBLEM WITH 1320 RINGS. HOWEVER MANY YOU GUYS COUNT!