How to Read a Motorcycle Chain Size Number
Motorcycle chain sizes are encoded in a three-digit code stamped on the outer plate of every chain. The code is not arbitrary — the first one or two digits encode the pitch (the distance between adjacent pins), and the last two digits identify the inner width family. Under JIS B 1801, the standard governing all motorcycle chain dimensions in Japan and Korea, these two values completely define sprocket compatibility requirements.
Decoding “428” and “520” — the two most common pitches
Applies to: 415, 420, 428
Specific to 428 family
Applies to: 520, 525, 530
Specific to 520 family
Note: width code numbers are identifiers — they do not convert directly to millimetres. Always verify against the published JIS B 1801 specification table.
The suffix letters after the base code identify the chain variant: no suffix = standard non-sealed; H = reinforced heavier plates; O = O-ring sealed; X = X-ring sealed; SX = Super X-ring sealed. So “525H-SX” is a 15.875 mm pitch, 7.94 mm inner width, H-grade reinforced Super X-ring sealed chain.
The width code is not a decimal measurement. “20” does not mean 2.0 mm — it identifies the 6.35 mm inner width family of the 520 series. Always use the published specification table rather than deriving measurements from the code number.
The Five Main Motorcycle Chain Sizes in Detail
Two pitch families cover all five sizes: the 12.700 mm (1/2-inch) family for smaller machines, and the 15.875 mm (5/8-inch) family for mid-range and larger machines. Within each pitch family, inner width varies to match the torque capacity and sprocket geometry requirements of different engine classes.
420 — Lightest in the 1/2-Inch Family
The 420’s 6.35 mm inner width makes it the narrowest of the 12.70 mm pitch family. At 0.57 kg/m, a 100-link 420 chain weighs approximately 570 g — for a 65–80 kg scooter, this chain weight relative to the machine’s total mass is more significant than it would be on a 200 kg touring bike. Fitting a 428 where a 420 is specified would add 140 g of rotating mass for no measurable strength benefit at 50–125cc power levels.
Inner width: 6.35 mm
Roller Ø: 7.77 mm
Tensile: 15,6 kN
Peso: 0.57 kg/m
Typical use: 50–125cc scooters, mini bikes
428 — The Most Widely Used Worldwide
The 428 is the highest-volume single chain size in the global aftermarket. Sharing pitch with the 420, it adds inner width (7.85 vs 6.35 mm) and roller diameter (8.51 vs 7.77 mm), giving a larger tooth contact area. The standard 428 at 17.8 kN covers most 125–250cc engines; the 428H at 20.6 kN handles the higher-output end without any sprocket change. Its versatility across dirt bikes, street bikes, scooters, dual-sports, and cruisers in the most populated displacement class makes replacement parts universally available.
Inner width: 7.85 mm
Roller Ø: 8.51 mm
Tensile: 17,8 kN
Peso: 0.71 kg/m
Typical use: 125–250cc street, dirt, enduro
520 — Lightest in the 5/8-Inch Family
The 520 moves to the 15.875 mm pitch family — longer pitch means larger roller contact radius at the sprocket tooth, distributing load over a greater arc. Its 6.35 mm inner width — the same as the 420 despite the longer pitch — makes it the narrowest and lightest of the three 5/8-inch variants at 0.91 kg/m. For sport bikes where minimising rotating mass matters, the 520 is the natural specification: a 520H-X at 34.0 kN gives sealed performance at a weight comparable to a standard 530.
Inner width: 6.35 mm
Roller Ø: 10.14 mm
Tensile: 26,5 kN
Peso: 0,91 kg/m
Typical use: 250–600cc sport, naked, inline-4
525 — The Balance Point Between 520 and 530
The 525’s 7.94 mm inner width is 1.59 mm wider than the 520 and 1.59 mm narrower than the 530. That wider roller provides more tooth-face contact area than the 520 — distributing load across a broader band of the sprocket tooth at a given chain tension. The trade-off versus the 520 is modest: 0.98 vs 0.91 kg/m, a difference of 70 g per metre. The 525 is typical OEM specification for adventure bikes, parallel-twin naked bikes, and sport tourers in the 650–750cc class.
Inner width: 7.94 mm
Roller Ø: 10.14 mm
Tensile: 26,5 kN
Peso: 0.98 kg/m
Typical use: 400–750cc adventure, naked twin
530 — Widest Standard, Highest Peak Strength
The 530’s 9.53 mm inner width makes the broadest tooth-face contact of the three 15.875 mm variants. At 1.09 kg/m for the standard, it is the heaviest — but on a 250 kg touring machine this is not a meaningful consideration. The strength advantage of the 530 family appears clearly in the SX-grade: the 530-SX at 43,0 kN is the highest tensile strength in the Korea Ever-Power range. For a fully-loaded touring motorcycle where combined mass exceeds 450 kg, the 530-SX’s structural margin over the working load is both technically sound and practically reassuring.
Inner width: 9.53 mm
Roller Ø: 10.14 mm
Tensile: 26.5 kN (530-SX: 43.0 kN)
Peso: 1.09 kg/m
Typical use: 600cc+ cruiser, tourer, large naked
All Five Sizes — Complete Specification Table
| Tamanho | Passo (mm) | Largura interna (mm) | Roller Ø (mm) | Standard Tensile | Top SX Tensile | Peso (kg/m) | Engine Class |
|---|---|---|---|---|---|---|---|
| 420 | 12.700 | 6.35 | 7.77 | 15,6 kN | — | 0.57 | 50–125cc scooter, mini bike |
| 428 | 12.700 | 7.85 | 8.51 | 17,8 kN | 28.0 kN (SX) | 0.71 | 125–250cc street, dirt, enduro |
| 520 | 15.875 | 6.35 | 10.14 | 26,5 kN | 36.0 kN (SX3) | 0.91 | 250–600cc sport, naked, MX |
| 525 | 15.875 | 7.94 | 10.14 | 26,5 kN | 40.0 kN (525-SX) | 0.98 | 400–750cc adventure, naked twin |
| 530 | 15.875 | 9.53 | 10.14 | 26,5 kN | 43.0 kN (530-SX) | 1.09 | 600cc+ touring, cruiser, large naked |
What You Can and Cannot Mix
Pitch determines sprocket tooth spacing — the 12.70 mm pitch chains (420, 428) will not engage correctly on 15.875 mm pitch sprockets, and vice versa. Within the same pitch family, inner width also must match the sprocket tooth gap. A 520 roller (6.35 mm wide) will not seat correctly in sprocket grooves designed for a 530 roller (9.53 mm wide) — the narrower roller sits between the tooth faces rather than against them, causing immediate abnormal wear.
✓ Change without new sprockets
- 420 → 420H (same pitch + width)
- 428 → 428H (same pitch + width)
- 428 → 428H-O or 428H-X (same)
- 520 → 520H, 520H-O, 520H-X (same)
- 525 → 525H, 525H-SX (same)
- 530 → 530H, 530H-O, 530-SX (same)
✗ Requires new sprockets
- 420 → 428 (different inner width)
- 428 → 520 (different pitch entirely)
- 520 → 525 (different inner width)
- 520 → 530 (different inner width)
- 525 → 530 (different inner width)
What you can always change freely within the same base size number: the chain variant suffix. Standard → H-grade → O-ring → X-ring → Super X-ring — all in the same base size (e.g. all “520” variants) — fit the same sprockets. The variant suffix changes the sealing system and plate gauge, not the pitch or inner width that determines sprocket compatibility. Upgrade at any chain replacement without touching the sprockets.
How to Find the Correct Size for Your Motorcycle
- 1Read the outer plate stamp — the size code is stamped on every chain’s outer plate. Read it directly: e.g., “428H” = 428-pitch H-grade. This is the definitive identification method.
- 2Check the service manual — every motorcycle’s owner’s manual or workshop manual lists the OEM chain specification under “drive chain” or “final drive.” This will include both size and standard link count.
- 3Send us the motorcycle details — make, model, and year. We identify the correct specification from our reference database and confirm before you order. No charge, no obligation.
Manufacturing Every Size to JIS B 1801
All five sizes — 420 through 530 — are produced on dedicated lines with pitch, inner width, roller diameter, and plate height verified against JIS B 1801 reference gauges before dispatch.
Korea Ever-Power Motorcycle Chain Co., Ltd. — five production facilities, ISO 9001 certified
Chain Sizes and Sprockets — All Pitches In Stock
Order single units or wholesale quantities. Stocked sizes dispatch within 3–7 business days. Mixed-size orders consolidated in one shipment.
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Perguntas frequentes
Confirm Your Chain Size Before You Order
Korea Ever-Power stocks all five pitches — 420 through 530 — in standard, H-grade, O-ring, X-ring, and Super X-ring. Send us your chain number or motorcycle model and we confirm the correct specification at no charge.
Full dimensional data for every size and variant on individual product pages.
Editor: Cxm
