77 express with mods

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.

Re: 77 express with mods

Soft seizes can sometimes cause ring snag or piston deformation which results in loss of compression.

Re: 77 express with mods

Check yo compression.

Re: 77 express with mods

and then get a temp gauge. (edited)

Re: 77 express with mods

Josh Hall /

after pulling the piston it turns out that i broke 3 of the 4 fins on the back side of the piston. ordered new redesigned piston from treats. Its aprently designed for better cooling and for better oil distribution.

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