Ive got a 77 express with a dr kit 20mm makuni and matching intake with big boss pipe. I took the bike out last sunday to break in the kit when it shut dow on me. The motor is free spinning but a little sluggish. I pulled the head off and did not see any scaring from a broken ring. I have not yet pulled the piston. I have good spark and good compression. Is it possilbe that without any scaring that the piston is screwed up and the motor is seized (soft)?? please help.