1989 Ski-Doo Repair Manual, Page 395Get this manual
Section 04 ELECTRICAL Sub-section 05 (ELECTRIC STARTER)
Brush length
Measure brush lengthIf less than the specified value, replace them
TROUBLESHOOTING
Causes of troubles are not necessarily related to the starter but may be due to faulty battery, switches, electrical cables andor connectionsConsult the following troubleshooting tableWARNING: Short circuiting the electric starter is always danger, therefore disconnect the ground cable at the battery before carrying out any kind of maintenance on the starting systemDo not place tools on battery