What was found
BTV---CO3055, AFTER TAKEOFF CREW REPORTED "LAV SMOKE (WARNING) AND VISIBLE CABIN SMOKE CLIMBING THROUGH 11000 FEET", DECLARED EMERGENCY AND AIR RETURNED BACK TO BTV, LANDED UNEVENTFULLY....MAINTENANCE REMOVED AIR TURBINE STARTER, REPLACED O-RINGS, AND REINSTALLED AIR TURBINE STARTER IAW RR AE3007 MM #80-10-01. OPS.CHECK AND LEAK CHECKED GOOD. AIRCRAFT RETURNED TO SERVICE.