Chinese 300cc 2-Stroke Engines: Five Manufacturers, Four in Chongqing, All 72×72

If you sell motocross motorcycles or parts in Russia, you have probably heard names such as Hengjian Z300, GR8, and GPX TSE300R. But who actually manufactures their engines? Five factories—four in Chongqing—all use the same basic platform. This article maps the manufacturers, specifications, and supply chain.

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The main conclusion

There are currently five manufacturers in China producing 300cc two-stroke motocross engines:

Four are in Chongqing and one is in Zhejiang. All use a 72×72 mm square-bore configuration. All are reverse-engineered from the KTM 300EXC.

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Why this matters

If you are a motocross dealer or parts seller in Russia, you need to understand three points:

1. Brand name ≠ engine manufacturer. GPX, GR8, Kamax, BRZ, and Avantis do not manufacture engines. They buy engines from the five factories listed above.
2. The same engine may appear under different brands. Hengjian FX300 powers the GPX TSE300R, GR8 2T 300, and Kamax K23. For parts ordering, the engine model matters far more than the motorcycle brand.
3. A shared 72×72 platform means many parts are interchangeable. Pistons, cylinders, crankshafts, and gearbox gears are substantially compatible across the five manufacturers. This is a major advantage for spare-parts inventory management.

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Manufacturer-by-manufacturer overview

1. Hengjian FX300—the largest volume and highest output

Hengjian is one of Chongqing’s most active motocross manufacturers and has the largest production volume for 300cc two-stroke engines.

The company developed the FX300, also known as the Z300, but does not cast it in-house. Manufacturing is contracted to a factory that holds the required production licence.

Market feedback points to the highest output in the group (42.6 kW), and the engine is used by major brands including GPX and GR8.

Key specifications:

• Bore × stroke: 72×72 mm
• Displacement: 293.2cc
• Maximum power: 42.6 kW (57.9 hp) at 8,500 rpm ← highest of the five
• Maximum torque: 52 N·m at 7,000 rpm ← highest of the five
• Compression ratio: 13.9:1 ← most aggressive
• Type: single cylinder / liquid cooled / two stroke / reed valve

Brands using the engine: GPX (USA), GR8 (Russia), and Hengjian’s own brand (SZC)

2. MIURA TS300

Key specifications:

• Bore × stroke: 72×72 mm
• Displacement: 293cc
• Maximum power: 38.5 kW (51.6 hp)
• Maximum torque: 43.5 N·m
• Compression ratio: 12.5:1
• Equipped with a balance shaft

Brands: Kamax, MIURA’s own brand, and others

3. Zhongmu TM300

Key specifications:

• Bore × stroke: 72×72 mm
• Displacement: 293cc
• Maximum power: 36 kW at 8,000 rpm
• Maximum torque: 43 N·m at 6,000 rpm
• Minimum fuel consumption: ≤354 g/kW·h
• Starting: electric and kick starter
• Clutch: manual, wet multi-plate

4. Koshine—the only Zhejiang manufacturer and the largest displacement

Koshine is based in Wuyi County, Zhejiang Province, and is the only manufacturer among the five located outside Chongqing.

Its 320cc two-stroke has the largest displacement in the group. Two versions are available: KE320 (standard) and KN320 (performance version).

Key specifications (KE320):

• Displacement: 320cc
• Maximum power: 30 kW at 8,500 rpm (about 42 hp)
• Maximum torque: 45 N·m at 8,000 rpm
• Carbon-fibre reed valve
• Six-speed gearbox

5. XFH XFH300-2

Key specifications:

• Bore × stroke: 72×72 mm
• Displacement: 300cc (293cc actual)
• Maximum power: 35 kW (47.6 hp)
• Maximum torque: 38 N·m
• Compression ratio: 11:1
• Distinguishing feature: imported crankshaft bearings

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Specification comparison

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Why the industry is concentrated in Chongqing

Chongqing has 51 motorcycle manufacturers and 410 parts manufacturers, with annual production capacity of 20 million engines.

Pistons, cylinders, crankshafts, and gearbox gears are all available within a 40-kilometre radius.