starting a Dutch wall clock again?

Chain came off sprocket when raising weight,turned clock upside down to fix, clock will not keep going,will work from 2 minuted to 2 hrs, have used spirit level to ensure level,have been fidling around now for 2 weeks, any sugestions, clock was completly overhauled 12 months ago
is hand made with German made time piece,standard clock chimes 1/2 and on hour,[ 2 weights] chimes part ok.

Mozza
December 2009