The Yokomo Masami Hirosaka Super Dog Fighter YZ 870C

Released in 1987, the YZ‑870C “Super Dog Fighter” became an off‑road icon. Developed in collaboration with world‑champion driver Masami Hirosaka, it debuted at the IFMAR 4WD Off‑Road Worlds in Ramsey, UK—finishing 4th—and went on to win the 1989 World Championship in St Ives, Australia under Hirosaka’s control. Domestically, it took the 1988 All‑Japan title, cementing its status as a performance stalwart .

Specifications:

• Chassis: FRP plate with 2‑belt drive and a vertical backbone .

• Suspension: Front/rear double wishbones with oil‑filled dampers and coil springs

• Transmission: Dual ball differentials, one‑way clutches, full ball bearings

• Bulkheads & knuckles: Magnesium originally, later redone in aluminum on the re‑release

• Wheels & tires: Standard original spec: 1.9″ spiked; modern setups run 2.2″

• Bodywork: Full reproduction of 1980s styling, including pinned rear wing

The YZ 870C excels in off-road terrain, thanks to its:

• High ground clearance: 55mm (2.2 in)

• Long-travel suspension: 30mm (1.2 in) of wheel travel

• Wide tire range: capable of handling various tire sizes and types

These features allow the YZ 870C to tackle challenging terrain, including rocks, sand, and jumps.  The chassis stiffness with upgraded top deck (in WC version) improves handling. The durable oil‑filled shocks, belt drive, and one‑way clutches provided smooth power delivery and traction.

The YZ 870C's build quality is exceptional, with a durable aluminum chassis and high-quality components. However, like any vintage RC buggy, it may require regular maintenance to ensure optimal performance. Original magnesium bulkheads and A‑arms were fragile; re‑release models had these upgraded to steel or aluminum. The stock springs tended to be too stiff thus owners often substitute softer modern springs. Despite occasional crashes, sturdier re‑release parts prevent total failure.

Some notable direct competitors include :

• Team Associated RC10/YZ‑10 (late 1980s): In the USA, the 870C was marketed as the Associated YZ‑10 (from 1988), featuring revisions. The YZ‑10 series later evolved into the YZ‑10 Works ’91 and ’93, but the 870C held its competitive edge through race success.

• Schumacher CAT XL, which Hirosaka raced in 1987.

To enhance the YZ 870C's off-road capabilities, consider the following modifications:

• Upgraded shock absorbers: Install modern, adjustable shock absorbers for improved suspension performance.

• Larger tires: Fit larger, more aggressive tires for increased traction and ground clearance.

• Brushless motor: Replace the original motor with a modern brushless motor for increased power and efficiency.

• Differential upgrade: Install a modern, adjustable differential for improved traction and handling.

• Suspension link upgrades: Upgrade suspension links to adjustable, aluminum links for improved suspension performance.

Additional improvements to maximise performance:

• Graphite upper deck - Increases chassis rigidity and handling consistency with no weight penalty.

• Aluminum shock towers - Boosts durability and prevents flex and fixes weak spots in crashes.

• Bearings-equipped steering bridge - Enhances precision and steering feedback for a crisp, direct steering feel.

• Aluminum front knuckles & C‑hubs - Strengthens suspension joints; sharper handling.

• Titanium turnbuckles & screws - Saves weight; improves durability.

• Softer modern springs - Tames overly stiff stock setup for better off‑road compliance.

• 2.2" modern wheels/tires - Larger contact patch for more grip and stability providing modern grip without body mods.

• Modern slipper clutch & diff - Improved power modulation and longevity; essential for handling brushless setups.

• Add motor fan - Keeps modern brushless motors cooler.

The Yokomo YZ‑870C Super Dog Fighter isn’t just historic—it’s a structurally sound platform that performs well even by modern standards. Its legendary origin story, race-proven durability, and smooth drivability make it a top pick among vintage RC enthusiasts. With targeted upgrades—particularly around chassis rigidity, suspension compliance, and reliability—it becomes not only a nostalgic treasure but also a competitive modern off‑road machine.