This manual covers JLO engines, specifically single and twin-cylinder models utilized in vintage snowmobiles. These engines, ranging from approximately 99cc to 600cc, powered various iconic snowmobile brands. The focus is on providing comprehensive information for maintaining and repairing these vintage powerplants, ensuring their continued operation for enthusiasts. This Service Repair Workshop Troubleshooting Manual in English offers detailed guidance for owners and technicians. It includes extensive troubleshooting, maintenance procedures for components like spark plugs and carburetors, overhaul instructions for engines and recoil systems, and technical data such as dimensional specifications and wiring diagrams. The manual is richly illustrated with diagrams and photos, making complex procedures easier to understand and execute.