Use the following troubleshooting table if you are encountering problems with bird nests and burrs.
Problem
Solutions
Bird nesting
Thread may be wrapped around the hook assembly. Check hook timing. (See Hook Timing Adjustment).
Check thread feed pinch roller - thread feed pinch roller is up or not seated correctly against thread feed roller.
Check rotary hook retaining finger - it could be too close to the rotary hook.
Burrs
Check the needle plate.