A sickle cutting system is mounted on a header for forward travel over ground having a standing crop thereon and includes a cutter bar with a plurality of knife guards and at least one sickle bar with a drive system for driving the sickle bar through repeated cycles of reciprocating movement from start-up of the system through to a shut-down. The drive system includes an arrangement to halt the sickle bar on shut-down at a predetermined position of the knife blades relative to the knife guards and preferably the position where the blades lie intermediate two knife guards. The system can be halted by either a physical stop member at the required position or by detecting the position of the sickle bar during operation and causing it to halt the required position. The detection can be carried out by counting pulses generated by markers on a rotary member of the drive system.
