OEM Stock Gearing - MX Mini Bikes

MX Parts Direct Technical Resource

OEM Mini Dirt Bike Stock Gearing Chart

Use this youth motocross and pit bike gearing reference chart to compare common OEM front sprocket, rear sprocket, chain pitch, and chain length information for popular 50cc, 65cc, 85cc, 110cc, 112cc, and CRF150R dirt bikes.

Important: This chart is for reference only. Always verify your exact year, model, wheel size, and current setup before ordering sprockets or chain. Previous owners may have changed gearing from stock, and some 85cc models use different gearing depending on standard-wheel or big-wheel configuration.

What the Numbers Mean

The front number is the countershaft sprocket tooth count. The rear number is the rear wheel sprocket tooth count.

Check Wheel Size

Many 85cc bikes are available in standard-wheel and big-wheel versions. The gearing and chain length may be different.

Chain Pitch Matters

Mini bikes may use 415, 420, or 428 chain. Match the chain pitch to both sprockets before ordering.

50cc OEM Stock Gearing

Make Model Year Range Front Rear Final Ratio Chain Notes
KTM 50 SX 2024-2026Verified 11 40 3.64 415 x 104 Current KTM 50 SX / Factory Edition stock-size reference.
Husqvarna TC 50 2022-2026Extended 11 40 3.64 415 x 104 Recent TC 50 stock-size reference carried forward; verify exact year.
GasGas MC 50 2024-2026Extended 11 40 3.64 415 x 104 Recent MC 50 stock-size reference carried forward; verify exact year.

65cc OEM Stock Gearing

Make Model Year Range Front Rear Final Ratio Chain Notes
KTM 65 SX 2026Verified 14 48 3.43 420 x 112 Current 2026 stock-size reference.
Yamaha YZ65 2026Verified 14 47 3.36 420 x 114 Current 2026 stock-size reference.
Kawasaki KX65 2022-2026Extended 13 47 3.62 420 x 110 Recent stock-size reference carried forward; verify exact year.
Husqvarna TC 65 2022-2026Extended 14 48 3.43 420 x 112 Recent TC 65 stock-size reference carried forward; verify exact year.
GasGas MC 65 2024-2026Extended 14 48 3.43 420 x 112 Recent MC 65 stock-size reference carried forward; verify exact year.

85cc OEM Stock Gearing

Make Model Year Range Front Rear Final Ratio Chain Notes
KTM 85 SX 17/14 2026Verified 13 46 3.54 428 x 124 Standard-wheel 85 SX reference.
KTM 85 SX 19/16 2026Verified 13 49 3.77 428 x 124 Big-wheel 85 SX reference.
Yamaha YZ85 2026Verified 14 46 3.29 428 x 118 Standard-wheel YZ85 reference.
Yamaha YZ85LW 2026Verified 14 51 3.64 428 x 124 Large-wheel YZ85 reference.
Kawasaki KX85 2026Verified 13 51 3.92 420 x 120 Current 2026 stock-size reference.
Suzuki RM85 2022-2026Extended 14 47 3.36 428 x 118 Recent RM85 stock-size reference carried forward; verify exact year.
Husqvarna TC 85 19/16 2026Verified 13 49 3.77 428 x 124 Big-wheel TC 85 reference.
GasGas MC 85 19/16 2025-2026Extended 13 49 3.77 428 x 124 Recent MC 85 big-wheel stock-size reference carried forward; verify exact year.

110cc / 112cc OEM Stock Gearing

Make Model Year Range Front Rear Final Ratio Chain Notes
Kawasaki KLX110R 2026Verified 13 38 2.92 420 x 90 Current KLX110R stock-size reference.
Kawasaki KLX110 / KLX110L 2010-2026Extended 13 38 2.92 420 x 90 Common current KLX110 platform reference; verify exact model year.
Kawasaki KX112 2026Verified 13 51 3.92 420 x 124 Current 2026 stock-size reference.

Honda CRF150R OEM Stock Gearing

Make Model Year Range Front Rear Final Ratio Chain Notes
Honda CRF150R 2026Verified 15 50 3.33 420 x 120 Standard-wheel CRF150R reference.
Honda CRF150R Expert 2026Verified 15 56 3.73 420 x 126 Expert / big-wheel CRF150R reference.

Mini Dirt Bike Gearing FAQ

What does 420 x 112 chain mean?

The first number is the chain pitch or chain size. The second number is the number of links. For example, 420 x 112 means a 420 chain with 112 links.

Why are some 85cc bikes listed twice?

Some 85cc models are sold in standard-wheel and big-wheel versions. These bikes may use different rear sprocket sizes and chain lengths, so it is important to confirm whether the bike is a 17/14 or 19/16 wheel model.

What does “Extended” mean in the chart?

Extended means the gearing is based on a current or recent stock-size reference and carried forward where the model platform appears consistent. Always verify your exact year and model before ordering.

Should I replace the chain when replacing sprockets?

For best performance and wear life, it is usually recommended to replace the chain and both sprockets together, especially if the current chain or sprockets show wear.

Is stock gearing always the best setup?

No. Stock gearing is a good starting point, but riders often change gearing based on track layout, rider size, skill level, corner speed, and how aggressively the bike needs to pull out of turns.

Need Help Finding Mini Bike Chain & Sprockets?

MX Parts Direct can help you find the right chain pitch, sprocket size, and gearing setup for youth motocross bikes, pit bikes, and race-ready mini bikes.

Shop Chains & Sprockets Ask Fitment Help

Fitment and OEM gearing information is provided as a reference only. Always consult your owner’s manual, OEM parts fiche, or current sprocket markings before purchasing. Regional models, special editions, big-wheel versions, and previous-owner modifications may vary.