| Specification | Data Value |
|---|---|
| Production Years | 2021–Present |
| Engine Type | Air-cooled Single Cylinder, SOHC |
| Oil Requirement | SAE 10W-30 JASO MA (2.1 L) |
| Front Tire | 100/90-19 M/C 57H |
| Rear Tire | 150/70R17 M/C 69H |
| Spark Plug | NGK LMAR8L-9 |
| Battery | YTZ7S |
The Honda GB 350 S (NC59A) represents a masterclass in modern-classic engineering. While many manufacturers opt for high-revving short-stroke engines, the NC59A platform features a unique long-stroke design (70mm bore x 90.5mm stroke). This specific geometry, paired with a heavy flywheel mass, was engineered to produce a distinct, tactile ‘thumping’ sensation—reminiscent of vintage British singles—while maintaining strict Euro 5 compliance through an offset cylinder design that minimizes friction.
Technical Engineering Overview
The ‘S’ variant distinguishes itself from the base GB 350 with sportier ergonomics and a 17-inch rear wheel (compared to the standard 18-inch), offering sharper turn-in and a wider selection of modern radial rubber. The powertrain utilizes Honda’s PGM-FI system and includes HSTC (Honda Selectable Torque Control), a rare feature in this displacement class that enhances safety on low-traction surfaces.
Maintenance Specifications
To maintain the longevity of the air-cooled NC59A engine, adherence to lubrication standards is critical. The engine requires 2.1 liters of SAE 10W-30 JASO MA oil. Honda specifically recommends the Ultra G1 formula to ensure optimal clutch performance and heat dissipation in the absence of a liquid cooling jacket.
Ignition and Electrical
The ignition system relies on a high-efficiency NGK LMAR8L-9 spark plug. Given the lean-burn nature of modern air-cooled engines, ensuring the gap is within spec is vital for cold-start reliability. The electrical system is powered by a compact YTZ7S battery, which should be maintained with a smart charger during long periods of storage to preserve the sensitive electronics of the HSTC system.
Chassis and Contact Patch
The ‘S’ model features a unique tire configuration: a 19-inch front for stability and a 17-inch rear for agility. Correct pressures are essential for handling neutrality. MotoSpecsLab recommends 2.0 bar (29 psi) in the front and 2.25 bar (33 psi) in the rear. These pressures balance the carcass stiffness required for the 150-section rear tire while maintaining comfort over urban irregularities.
Expert Verdict
The Honda GB 350 S is not merely a retro exercise; it is a sophisticated piece of mechanical engineering that prioritizes ‘feeling’ over raw horsepower. For the owner-mechanic, it offers a refreshing simplicity, though the inclusion of modern electronics requires a disciplined approach to battery and sensor maintenance.