| Component | Specification |
|---|---|
| Model Year | 1985 |
| Engine Oil | SAE 10W-40 / 20W-40 (2.1 L) |
| Front Tire | 3.00-21 51P (1.5 bar / 22 psi) |
| Rear Tire | 4.60-18 63P (1.5 bar / 22 psi) |
| Spark Plug | NGK DPR8EA-9 (0.8–0.9 mm gap) |
| Battery | YB5L-B (12V) |
The 1985 Yamaha XT 600 Z, designated as the 55W, holds a unique position in dual-sport history as the ‘bridge’ model of the Ténéré lineage. While many enthusiasts focus on the 34L or the later 1VJ, the 55W is engineered with a specific highlight: it was the final iteration to utilize the highly reliable gravity-fed fuel system combined with a slightly shortened 28-liter tank, effectively solving the fuel-starvation issues that occasionally plagued the larger-tank prototypes under extreme heat.
Engineering Overview
At the heart of the 55W is the 595cc SOHC four-valve air-cooled single. This engine is legendary for its torque delivery and the YDIS (Yamaha Dual Intake System), which uses a primary carburetor for low speeds and a secondary vacuum-operated carburetor for high-speed airflow. This setup provides the 55W with a level of fuel efficiency and throttle response that defined the Paris-Dakar era of the mid-80s.
Maintenance Guide & Technical Data
Maintaining the 55W requires strict adherence to its air-cooled thermal limits. The oil capacity is 2.1 liters, and because the engine relies heavily on oil for cooling, using a high-quality mineral or semi-synthetic SAE 10W-40 or 20W-40 (API SE/SF) is critical. Owners should check the oil level via the frame tank dipstick only after the engine has reached operating temperature and idled for several minutes.
For the ignition system, the NGK DPR8EA-9 is the standard. Ensuring a precise gap of 0.8–0.9 mm is vital for cold starts in high-humidity environments. The electrical system is powered by a YB5L-B battery; given the age of these machines, checking the charging circuit output is a recommended annual task.
Chassis and Handling
The 55W features the Monocross rear suspension with a Link-type system that offers significant travel for off-road excursions. Tire pressures should be maintained at 1.5 bar (22 psi) for balanced use, though off-road specialists may drop the rear pressure slightly for improved traction in soft sand, provided rim locks are installed.
Frequently Asked Questions
How much oil does the XT 600 Z 55W hold?
The total oil capacity for a change with filter is 2.1 Liters. Always use API SE/SF rated oils or higher to protect the gearbox and wet clutch.
What are the correct tire sizes?
The factory specifications are 3.00-21 51P for the front and 4.60-18 63P for the rear, providing a classic narrow-profile footprint for better tracking in dirt.
Can I use a different spark plug?
While alternatives exist, the NGK DPR8EA-9 is the heat range specifically engineered for the 595cc single-cylinder’s combustion chamber temperature.