rear hydraulic

hi all
i have fitted a rear hydraulic on scoot and the pads lock onto disc and locks up back wheel, its a saigon scoot one, i hadproblem last year then changed caliper and it was fine, had new engine fitted so dismantled everything but kept hose etc in tact, scoot sat for 7 months and its happening again
i have fitted a rear hydraulic on scoot and the pads lock onto disc and locks up back wheel, its a saigon scoot one, i hadproblem last year then changed caliper and it was fine, had new engine fitted so dismantled everything but kept hose etc in tact, scoot sat for 7 months and its happening again