Automatic decompressor

Automatic decompressors are sometimes equipped to pull-start starters.
During starting, the decompression pin attached to the camshaft is pushed in by the flyweight, which in turn pushes up the tappet just before compression top dead center, temporarily opening the exhaust valve so that compression pressure can be released.
This enables the recoil rope to be pulled with a lighter force. When the engine is started and its speed increased, centrifugal force opens the flyweight outward, causing the decompression pin to drop.
This enables the exhaust valve to open and close normally.

Search by acronym