Honda CB400 Four (1974-1978) Review: The Gentleman's Four-Cylinder Classic

Introduction

The Honda CB400 Four stands as one of motorcycling's most elegant answers to the question: "What if we made a small-displacement bike feel premium?" Produced from 1974 to 1978, this 405cc inline-four masterpiece arrived at a time when manufacturers were focused on either raw power or utilitarian simplicity. Honda took a different path - crafting a motorcycle that combined technical sophistication with everyday usability. Even today, riding a well-maintained CB400 Four feels like discovering a perfectly preserved time capsule of 1970s engineering philosophy.

Design & Styling

The CB400 Four's design language walks a tightrope between sporty aggression and classic restraint. Its teardrop fuel tank (14-liter capacity) flows into a gently rising seat line, while the chrome accents on the exhaust system and engine covers add just enough flash without appearing gaudy. The 790mm seat height (31.1 inches) makes it accessible for riders of various statures, though the 184kg (405 lb) wet weight reminds you this isn't some featherweight commuter.

Modern riders will appreciate details like: - Analog gauges with crisp white-on-black numbering - Rubber-mounted footpegs reducing vibration - Generous chrome fenders offering real-world protection - A center stand that's actually usable (a rarity today)

The real showstopper is the engine itself - Honda's smallest four-cylinder powerplant ever mass-produced. Those four gleaming exhaust headers curving under the engine create visual drama missing from modern single- and twin-cylinder counterparts.

Engine & Performance

At its heart lies the 405cc DOHC inline-four (53.0 x 45.4mm bore/stroke) producing 37 PS (27 kW) at 9,500 RPM. These numbers seem modest today, but the experience is anything but:

• 0-100 km/h (0-62 mph): ~14 seconds
• Top Speed: 160 km/h (100 mph) indicated
• Fuel Consumption: ~18-22 km/l (42-52 mpg)

The magic lies in the delivery. Unlike modern high-strung fours, the CB400 builds power linearly from 3,000 RPM, hitting its sweet spot between 6,000-9,000 RPM. The 17/38 sprocket combination (paired with 96-link chain) provides relaxed highway cruising at 110 km/h (68 mph) with the tach needle hovering around 7,500 RPM.

Key maintenance specs: - Valve Clearances: 0.08-0.18mm (0.003-0.007 in) cold - both intake/exhaust - Idle Speed: 1,050 ±50 RPM - Spark Plugs: NGK DR8ES (standard) or DR8EIX (iridium upgrade) - Oil Capacity: 3.5L (3.7 qt) with filter change

Riding Experience

Swing a leg over the CB400 Four, and you're immediately struck by its ergonomic neutrality. The handlebars rise just enough to avoid wrist strain, while the slightly rear-set pegs let you hug the tank during spirited riding. The air-cooled engine pumps out noticeable heat at stops - a character trait rather than a flaw.

The 33mm telescopic forks (145-150ml SAE 10W oil) and twin shock rear suspension feel plush over minor imperfections but require careful setup for aggressive riding. Braking performance from the single 260mm front drum and rear drum is... adequate. Modern riders should: 1. Upgrade to sintered brake shoes 2. Maintain DOT 4 fluid religiously 3. Adjust expectations for stopping distances

Tire pressures (1.8 bar/26 psi front, 2.0-2.5 bar/29-36 psi rear) work best with period-correct rubber, though many owners now fit modern radials with revised pressure settings.

Competition

The CB400 Four existed in a golden era of middleweight standards. Key rivals included:

1. Kawasaki Z400 (1974-1976) - Twin-cylinder, 398cc - 44 PS (32 kW) - more peak power - Heavier vibration - Less refined transmission Today's Edge: CB400's four-cylinder smoothness ages better

2. Yamaha XS400 (1976-1979) - Parallel-twin, 391cc - 34 PS (25 kW) - Softer suspension setup - Better fuel economy Today's Edge: CB400's parts availability remains superior

3. Suzuki GS400 (1976-1979) - Twin-cylinder, 398cc - 35 PS (26 kW) - Oil-cooling system - More complex maintenance Today's Edge: CB400's air cooling simplifies ownership

While competitors often offered more power or lower prices, none matched the Honda's blend of mechanical sophistication and long-term usability. Modern collectors particularly value the CB400 Four's uniqueness - it's the only Japanese four-cylinder 400cc bike of its era.

Maintenance & Ownership

Owning a CB400 Four in 2024 requires understanding its 1970s maintenance rhythms:

1. Valve Adjustments Every 3,000 km (1,864 miles): - Check clearances using 0.08-0.18mm feeler gauges - Replace valve cover gasket if leaking (MOTOPARTS Recommendation: Use Honda-bond HT for gasket sealing)

2. Carburetor Care The four Keihin carbs demand synchronization every 6,000 km: - Set air screws to 2 turns out (baseline) - Clean pilot jets annually - Consider ethanol-resistant fuel lines

3. Chain Maintenance The 96-link chain needs: - Adjustment every 500 km (310 miles) - Regular lubrication with 80W-90 gear oil - Replacement when stretch exceeds 2%

4. Electrical Upgrades Common improvements: - Modern solid-state regulator/rectifier - LED bulbs (6V system compatible) - AGM battery conversion

5. Critical Fluids - Engine Oil: SAE 10W-40 (3.5L/3.7 qt) - Fork Oil: SAE 10W (145-150ml per leg) - Brake Fluid: DOT 4 (annual flush)

Legacy & Modern Appeal

What makes the CB400 Four endure when so many contemporaries faded into obscurity? It's the motorcycle equivalent of a mechanical wristwatch - complex not because it needs to be, but because it can be. The inline-four's turbine-like smoothness still impresses riders raised on twins and singles, while the overall package remains manageable for new collectors.

Modern customization trends have been kind to the CB400 Four. Popular mods include: - 4-into-1 exhaust systems (with jetting kits) - Progressive rate suspension springs - Dual-disc front brake conversions - Café racer tail sections

Yet even in stock form, this Honda possesses a timeless quality. The engine's 405cc displacement (conveniently under many countries' 400cc learner restrictions) makes it globally relevant, while the parts support from specialists like MOTOPARTS.store ensures these bikes keep running better than new.

Conclusion

The CB400 Four isn't the fastest, lightest, or most technologically advanced motorcycle ever made. What it offers is something rarer - a chance to experience Honda's engineering prowess in its purest form. From the valve adjustment process (where you get intimate with all 16 tappets) to the way the four-cylinder purr evolves into a metallic howl at full chat, every aspect feels deliberate and crafted.

For owners and restorers, MOTOPARTS.store carries essential maintenance items: - Complete gasket kits - Carburetor rebuild bundles - Period-correct brake components - Engine guard bars - Vintage-style tires

Whether you're preserving a concours example or building a restomod café racer, the CB400 Four remains one of motorcycling's most rewarding mechanical partners. Its blend of accessibility and sophistication ensures that nearly 50 years after its debut, this Honda still feels special in a way few modern bikes can match.

---

Specifications sheet

---