2018 Yamaha ZUMA 50FX Service and Repair Manual
2018 is the final model year within the scope of LIT-11616-27-46, and the ZUMA 50FX built that year carries the code YW50FXJR.
Yamaha's book gives you specifications and service intervals, engine procedures with disassembly order and inspection measurements, automatic transmission and final drive work, chassis and brake service, torque specifications, full wiring diagrams with component test values, and troubleshooting organised by symptom.
On a late-run machine the inspection limits do the most work. They tell you whether a belt, a roller or a bearing is still within tolerance, which keeps a service from turning into a parts order. The wiring diagrams matter for the same reason: measuring a circuit beats replacing components to find the fault.
Verify YW50FXJR against your frame before buying, and note LIT-11616-27-46 as the literature number for this manual.