Καδένα χρονισμού μοτοσικλέτας *25 *25H *25SH σειρά 06B

ΕΝΑ motorcycle timing chain is the mechanical link between the crankshaft and the camshaft inside a four-stroke engine. Its job is precise: the crankshaft rotates twice for every one full combustion cycle, and the camshaft must rotate at exactly half that speed so the intake and exhaust valves open and close at the right moment relative to piston position. If these timings drift — even slightly — fuel economy drops, power falls, and in severe cases valve-to-piston contact occurs at high rpm.

Unlike the rear drive chain on the outside of the engine, the timing chain operates inside a sealed oil-wet environment. It is lubricated continuously by the engine's own oil system, requires no external maintenance from the owner, and is managed by an automatic hydraulic or spring tensioner that compensates for chain wear over time. When a timing chain does reach the end of its service life, the symptoms are measurable and audible: a rattling noise on cold startup from the timing cover, slight valve timing retardation that shows up as mild power loss, and in advanced wear, an intermittent misfire as the chain skips a tooth under load.

Korea Ever-Power Motorcycle Chain Co., Ltd. supplies timing chains across three pitch sizes — 6.350 mm, 7.774 mm, and 9.525 mm — covering the *25, *25H, *25SH, 05H-1, *219HT, *BF05T, 06BH, 06BT, 06B, *35, and *C35 series. These are the pitch families most commonly found in small to medium displacement four-stroke αλυσίδες μοτοσικλέτας and engine applications.

The table covers all timing chain series in our range. Transverse pitch (Pt) applies only to the double-strand variants (06BT-2, *35-2, *C35*2, 06B-2); single-strand chains leave this cell blank. Ultimate tensile strength (Q min) is the minimum guaranteed break load; average tensile strength (Q0) reflects the mean across tested samples from each production batch.

The terms "timing chain" and "cam chain" both refer to the engine's valve timing drive, but the chain type varies by engine design. Roller timing chains (the *25, 06B, *35 series above) and silent chains (the CL04 series covered separately) serve the same function through different mechanical approaches. Knowing which type your engine uses matters when sourcing a replacement — the sprocket tooth profiles differ between the two types and are not interchangeable.

To confirm which type your engine uses, look through the oil filler cap opening with the engine warm or remove the timing cover with proper tools — roller chains are immediately distinguishable by their round rollers between the plates. The service manual for your motorcycle will specify the chain series number, pitch, and link count required for replacement.

Understanding how the timing chain translates crankshaft rotation into precise valve movement helps clarify why chain condition affects every aspect of engine performance:

Motorcycle timing chains are designed to last the engine's full service life — typically 100,000–160,000 km — but poor oil maintenance or high-output engine modifications can shorten this considerably. Watch for these specific indicators:

To extend timing chain life: change engine oil at or before the manufacturer's recommended interval using the correct viscosity grade; avoid prolonged idling immediately after a cold start (allow 60–90 seconds for oil pressure to build before riding); and avoid high-rpm use until the engine reaches operating temperature. These three habits together have more effect on chain longevity than any other single maintenance factor.

Three sprockets are typically involved in a motorcycle's timing drive: the crankshaft sprocket, the camshaft sprocket (one per cam in DOHC engines), and in some designs an intermediate or tensioner idler sprocket. All three are manufactured to precise tolerances — the tooth profile, pitch, and diameter must match the chain specification exactly.

Crankshaft sprocket: Located at the end of the crankshaft, this is the smallest sprocket and drives the chain. Its tooth count determines the base timing ratio. Because it is the smallest and fastest-rotating sprocket in the timing system, it typically wears fastest. Any score marks on the tooth faces or visible rounding of the tooth tips indicates replacement is due.

Camshaft sprocket: Fixed to the camshaft end, this is larger than the crankshaft sprocket — typically 2:1 tooth ratio. On variable valve timing (VVT) engines, the cam sprocket incorporates a hydraulically-actuated phaser mechanism. Replacement of the cam sprocket requires the phaser to be tested or replaced simultaneously.

Intermediate sprocket: Some multi-cylinder engine designs route the timing chain through an additional guide or idler sprocket to clear obstructions or control chain tension geometry. This sprocket bears the chain's back-side load and wears on the non-drive face of its teeth — a different wear pattern from the drive sprockets. Inspect it carefully when inspecting the chain.

Replacing chain sprockets as a complete set with the chain is standard practice — individual components worn to match each other will not wear a new chain or sprocket evenly, accelerating the failure of whichever part was renewed alone.

Korea Ever-Power Motorcycle Chain Co., Ltd. supplies both roller-type timing chains (the series covered on this page) and silent chains (CL04 series) for motorcycle engine applications. Our manufacturing network operates ISO 9001 certified quality management with dedicated controls for engine-application chains: dimensional inspection of pitch, roller diameter, and inner plate height against reference gauges; tensile testing by production batch; and articulation inspection before packing. Contact us with your engine model number and current chain part number for cross-reference confirmation before ordering.

How is a timing chain different from the rear drive chain?
The rear drive chain is external to the engine, transfers power from the engine output shaft to the rear wheel, requires periodic external lubrication and tension adjustment by the owner, and is replaced every 15,000–30,000 km depending on type. A timing chain sits inside the engine, is lubricated by engine oil automatically, has its tension managed by an automatic tensioner, and is designed to last 100,000+ km. The two serve completely different mechanical functions and are not interchangeable in any dimension.

Can I replace only the timing chain without replacing the sprockets?
Technically possible, but not recommended in most cases. If the sprockets show any tooth wear — even mild rounding — the worn sprocket profiles will impose uneven load on the new chain's rollers, accelerating wear. If the existing sprockets are genuinely unworn (common in low-mileage replacement scenarios), the chain-only replacement is acceptable. Inspect sprocket tooth profiles before deciding.

Does oil grade affect timing chain life?
Yes, significantly. The timing chain relies on oil film between the roller and sprocket surfaces and between chain links to prevent metal-to-metal contact. Thin oil at high operating temperatures — which occurs when using incorrect viscosity grades — reduces this film thickness. Using the manufacturer's specified oil type and changing it at or before the recommended interval is the single most effective protection for the timing chain.

What is the *25 vs *25H vs *25SH difference?
All three share the same 6.350 mm pitch and inner width. The *25 is the standard variant at 3.50 kN minimum tensile strength, 0.14 kg/m. The *25H upgrades tensile strength to 4.80 kN minimum with longer pin length (9.00 vs 7.80 mm) and heavier weight (0.18 kg/m). The *25SH achieves 5.20 kN minimum — the highest in the 6.350 mm family — with a smaller pin diameter (2.01 vs 2.31 mm), suggesting a different alloy or heat treatment approach to reach higher strength at reduced pin section. Confirm the original specification from the motorcycle's parts list before substituting between variants.

How do I identify which timing chain series my engine uses?
The most reliable approach is the motorcycle's official parts list or service manual, which specifies the part number and chain dimensions. If the original chain is removed and accessible, measure the pitch (pin-centre to pin-centre distance) and the inner width — these two figures narrow the selection to one or two series. Contact us with the engine model, year, and measured dimensions for cross-reference confirmation.

Kim Dong-jae, Engine Rebuild Technician, Seoul (February 2025)
"Used the 06BT-l for a cam chain replacement on a 150cc single-cylinder rebuild. Dimensions matched the OEM specification exactly — pitch, inner width, and roller diameter all checked out with callipers before installation. Engine runs quietly post-rebuild. Korea Ever-Power responded quickly to confirm compatibility before I ordered."

Oh Se-jun, Independent Workshop Owner, Daejeon (January 2025)
"We do a lot of high-mileage engine refreshes on commuter bikes. The *25H is our standard replacement for engines that originally spec it. Consistent dimensional quality across three batch orders — no surprises at installation. Tensile strength testing data provided on request, which not all suppliers offer."

Park Joon-gi, Motorcycle Restorer, Busan (November 2024)
"Restoring a 1990s 250cc twin that uses 06B-1. Hard to source locally. Korea Ever-Power confirmed the specification match and shipped promptly. Chain installed correctly and engine timing checked to spec on a strobe light — no deviation from factory timing marks."

Lee Sang-woo, Fleet Maintenance Engineer, Incheon (March 2025)
"Managing a fleet of 50cc scooters that use *25 series timing chains. High turnover maintenance operation — we need consistent supply and predictable quality. Korea Ever-Power's batch quality has been uniform across our last four orders. No fit issues and no post-install failures in 6 months of tracking."