The interior of the Makita 4190D Kitty Hawk saw was severely corroded by water, and the motor was stuck by rust. The metal parts are sandblasted to remove rust, repainted or blackened with blackening liquid to prevent rust. Fixed broken shell The battery was partially disassembled and replaced with three strings of 21700 cells. Eventually full functionality was restored. The metal parts of early Makita tools were relatively weak in rigidity, so when disassembling them, attention should be paid to protecting the gears and spindles.