Here are some documents and images to provide you with more technical information.

Ossa Service Bulletins

Clearance Chart

Transmission Gear Information

Ignition Timing Chart

Ignition Timing Settings

Ignition Motoplat Facts

Trasmission / Fork Oil Capacities

Ossa Bolt Size

OSSA Port maps/ Schematics

Spark Plugs

Ossa 5-Speed Manual

Ossa 4-Speed Manual

Side Cover Screw Diagrams

OSSA-Yankee Wiring Diagrams

Parts Diagram by Model