| Parameter | Specification |
|---|---|
| Production Years | 1985-1986 |
| Engine Type | Air-cooled, 4-cylinder, DOHC |
| Oil Type | SAE 10W-40 / 20W-40 (2.8 L) |
| Spark Plug | NGK BPR8ES |
| Battery | YB14L-A2 |
| Front Tire | 100/90-18 56V (2.25 bar) |
| Rear Tire | 120/90-18 65V (2.5 bar) |
The Yamaha XJ 900 N (58L) occupies a unique niche in motorcycling history as one of the final expressions of the ‘Universal Japanese Motorcycle’ (UJM) philosophy before the industry shifted toward specialized fairings and sport-touring plastics. While the faired ‘F’ model gained popularity for touring, the ‘N’ (Naked) version is technically significant for its YICS (Yamaha Induction Control System), which improved combustion efficiency and fuel economy, making it one of the most refined air-cooled inline-fours of the mid-1980s.
Engineering and Performance
At the heart of the 58L is a 853cc air-cooled engine that delivers power through a low-maintenance shaft drive. Unlike its predecessors, the 58L benefited from revised carburetor settings and improved frame geometry, providing a more stable ride at high speeds. The naked configuration allows for easier cooling of the rear cylinders, a common pain point in faired multi-cylinder bikes of that era.
Maintenance Essentials
Lubrication System
For optimal engine longevity, MotoSpecsLab recommends using a high-quality mineral or semi-synthetic SAE 10W-40 or 20W-40 oil meeting API SG and JASO MA standards. The total refill capacity is 2.8 liters. Given the air-cooled nature of the engine, regular oil changes every 5,000 km are vital to prevent thermal breakdown.
Ignition and Electrical
The XJ 900 N utilizes NGK BPR8ES spark plugs. Ensure the gap is set correctly to maintain the smooth idle characteristic of the YICS system. The electrical system is supported by a YB14L-A2 lead-acid battery; owners should regularly check electrolyte levels due to the heat generated by the engine block.
Tires and Handling
The 58L handles best with its original staggered 18-inch wheel setup. We specify a 100/90-18 front and a 120/90-18 rear. Maintaining precise pressures of 2.25 bar (33 psi) front and 2.5 bar (36 psi) rear is critical to prevent the ‘low-speed weave’ sometimes associated with older shaft-drive chassis.
Reliability and Verdict
The Yamaha XJ 900 N 58L is a testament to over-engineering. Its shaft drive is nearly bulletproof if the gear oil is changed periodically, and the valve clearances (shim-over-bucket) stay in spec for surprisingly long intervals. For the modern collector or vintage rider, the 58L offers a raw, mechanical connection that faired bikes of the same era simply cannot match.