Motocross

KTM 150 SX 2025

Motocross, 150cc 2T, EU version

Verified

Illustration: a KTM motocross bike, not this exact model.

From the owner’s manual: premix 40:1, p. 33; coolant 1.2 l (1.3 qt.), p. 133; front tire 80/100-21 51M TT, p. 135; rear tire 100/90-19 57M TT, p. 135. Checked 25 Sep 2026.

Model year on file: 2025 only. Other years are added as their manuals are read.

No CPSC recall found for the 2025 KTM 150 SX, checked 2026-10-15. Recalls

Spec card PDF

Gearing

4 of 5 filled

Stock front sprocket: 13T; Verified, read off the manual page: Manual p. 134 · checked 2026-09-25 source [2]
Stock rear sprocket: 48T; Verified, read off the manual page: Manual p. 134 · checked 2026-09-25 source [2]
Chain pitch: 520; Calculated, not printed: The trade name of the printed size 5/8 x 1/4" · Manual p. 134 · checked 2026-09-25 source [2]
Stock chain links: Not yet verified
Stock final drive ratio: 3.69 : 1; Calculated, not printed: Calculated from the stock sprockets, printed on manual p. 134

Wheels and tires

2 of 4 filled

Front rim: Not yet verified
Rear rim: Not yet verified
Front tire: 80/100-21 51M TT; Verified, read off the manual page: Manual p. 135 · checked 2026-09-25 source [2]
Rear tire: 100/90-19 57M TT; Verified, read off the manual page: Manual p. 135 · checked 2026-09-25 source [2]

Suspension

6 of 7 filled

Fork: WP XACT air fork (air spring left leg, damping right leg); Verified, read off the manual page: Manual p. 42 · checked 2026-09-24 source [1]
Fork travel: 310 mm (12.2 in); Verified, read off the manual page: Manual p. 134 · checked 2026-09-25 source [2]
Shock travel: 300 mm (11.81 in); Verified, read off the manual page: Manual p. 134 · checked 2026-09-25 source [2]
Stock fork spring rate: Not yet verified
Stock shock spring rate: 39 N/mm; Verified, read off the manual page: Manual p. 41 · checked 2026-09-24 source [1]
Static sag, bike only: 35 mm (1.38 in); Verified, read off the manual page: Manual p. 39 · checked 2026-09-24 source [1]
Race sag, rider on: 105 mm (4.13 in); Verified, read off the manual page: Manual p. 39 · checked 2026-09-24 source [1]

Fluids and capacities

3 of 3 filled

Coolant capacity: 1.2 l (1.3 qt.); Verified, read off the manual page: Manual p. 133 · checked 2026-09-25 source [2]
Premix ratio: 40:1; Verified, read off the manual page: Manual p. 33 · checked 2026-09-24 source [1]
Fuel capacity: 7.2 l (1.9 US gal); Verified, read off the manual page: Manual p. 133 · checked 2026-09-25 source [2]

Maintenance

3 of 3 filled

Tire pressure (off-road): 1.0 bar (15 psi) front and rear; Verified, read off the manual page: Manual p. 136 · checked 2026-09-25 source [2]
Chain slack: 58-61 mm (2.28-2.4 in); Verified, read off the manual page: Manual p. 76 · checked 2026-09-25 source [2]
Spark plug and gap: NGK BR10 ECMVX, gap 0.80 mm; Verified, read off the manual page: Manual p. 133 · checked 2026-09-25 source [2]

Dimensions

3 of 3 filled

Seat height: 958 mm (37.72 in); Verified, read off the manual page: Manual p. 134 · checked 2026-09-25 source [2]
Wheelbase: 1493 mm (≈ 58.8 in, converted by MotoXSports); Verified, read off the manual page: Manual p. 134 · checked 2026-09-25 source [2]
Weight: 92.1 kg (203 lb.); Verified, read off the manual page: Manual p. 134 · checked 2026-09-25 source [2]

Service specs

0 of 6 filled

Gearbox oil, fork oil, brake fluid, coolant type, fuel octane, idle speed: Not yet verified

Solid marks are owner's-manual pages; hollow marks are manufacturer web or spec-sheet figures still waiting on a manual page. Last reviewed 2026-09-25. Rows marked not yet verified are blank on purpose.

Buying parts

The stock sizes and specs this bike left the factory with, each with its source. Take them to any shop.

Retailer links below are affiliate links: we may earn a commission, at no cost to you, and it never changes the specs. Affiliate disclosure.

Chain: Chain pitch 520 Owner's manual p. 134520 chains at MotoSport 520 master links at MotoSport
Sprockets: Stock front sprocket 13T Owner's manual p. 134Stock rear sprocket 48T Owner's manual p. 13413T front sprockets at MotoSport 48T rear sprockets at MotoSport
Tires: Front tire 80/100-21 51M TT Owner's manual p. 135Rear tire 100/90-19 57M TT Owner's manual p. 135Front tires 80/100-21 at MotoSport Tubes 80/100-21 at MotoSport Rear tires 100/90-19 at MotoSport Tubes 100/90-19 at MotoSport
Coolant: Coolant capacity 1200 ml (40.6 fl oz) Owner's manual p. 133Coolant at MotoSport
Suspension springs: Stock shock spring rate 39 N/mm Owner's manual p. 41Suspension at MotoSport

In stock at MotoSport

Prices from MotoSport’s catalog of Oct 26, 2026; check today’s price before you buy.

Front tire, stock size 80/100-21

Rear tire, stock size 100/90-19

Prices and stock from MotoSport's product catalog on Oct 26, 2026; they change, so check the price at MotoSport before you buy. Products are chosen by exact stock size, code or oil viscosity from the specs above, known brands first, then price. We have not tested them.

2 part specs not yet verified; see data coverage.

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Gearing calculator

Gearing for this bike

Put your current gearing in Setup A and the setup you are considering in Setup B. Everything updates as you type.

Start from a bike's stock gearing

Pick a bike to fill both setups with its stock sprockets.

Front sprockets 8–16 teeth, rear 34–60. Values outside that range are brought back to the nearest limit.

Setup A — what you run now

Front teeth

Rear teeth

Setup B — what you are thinking about

Front teeth

Rear teeth

Final drive ratio

— — : 1

—

Pull at the wheel—

Top speed—

Ratio change—

A —

B —

Taller · more speed Shorter · more pull

—

Changing the rear sprocket changes the chain length too. The chain length calculator works it out from the chain you have now, with where the axle ends up.

Ratios are exact. The chain figure is an estimate of roughly one link per two teeth of change — confirm against your manual before ordering.

What's missing

20 of 30 fields read off a manual page.

Not yet verified (10): chain links, front rim, rear rim, fork spring rate, gearbox oil, fork oil, brake fluid, coolant type, fuel octane, idle speed.

See coverage for every bike

Sources

1
KTM Owner's Manual 2025 125 SX / 125 XC / 150 SX, Art. no. 3240041en (17.04.2024); copy hosted by a KTM dealerpp. 33, 39, 41, 42Manual page, verified. Covers fork, stock shock spring rate, static sag, bike only, race sag, rider on, premix ratio; checked 2026-09-24.
2
KTM Owner's Manual 2025 125 SX / 125 XC / 150 SX, Art. no. 3240041en; owner-supplied copy, same document as the dealer-hosted PDFpp. 76, 133, 134, 135, 136Manual page, verified. Covers stock front sprocket, stock rear sprocket, chain pitch, fork travel, shock travel, seat height, wheelbase, weight, front tire, rear tire, coolant capacity, fuel capacity, tire pressure (off-road), chain slack, spark plug and gap; checked 2026-09-25.

Always confirm against the manual for your exact year before ordering parts or setting up suspension. Torque specs are deliberately not published here. How we verify a value.

Your manual prints something different? Report a value with the page it is on; every fix is listed in the corrections log.

My settings

Date / track
Sprockets run
Race sag / free sag
Fork air pressure or spring
Fork clickers (compression / rebound)
Shock clickers (low / high / rebound)
Tire pressures (front / rear)
Notes

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