Motocross

KTM 85 SX 2027

Motocross, 85cc 2T, US version

Verified

From the owner’s manual: premix 40:1, p. 126; coolant 0.8 l, p. 122; front tire 70/100-17 M/C 40M TT, p. 126; rear tire 90/100-14 M/C 49M TT, p. 126. Checked 16 Oct 2026.

Model year on file: 2027 only. Other years are added as their manuals are read.

No CPSC recall found for the 2027 KTM 85 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. 125 · checked 2026-09-28 source [1]
Stock rear sprocket: 46T; Verified, read off the manual page: Manual p. 125 · checked 2026-09-28 source [1]
Chain pitch: 428; Calculated, not printed: The trade name of the printed size 1/2 x 5/16" · Manual p. 125 · checked 2026-09-28 source [1]
Stock chain links: Not yet verified
Stock final drive ratio: 3.54 : 1; Calculated, not printed: Calculated from the stock sprockets, printed on manual p. 125

Wheels and tires

2 of 4 filled

Front rim: Not yet verified
Rear rim: Not yet verified
Front tire: 70/100-17 M/C 40M TT; Verified, read off the manual page: Manual p. 126 · checked 2026-09-28 source [1]
Rear tire: 90/100-14 M/C 49M TT; Verified, read off the manual page: Manual p. 126 · checked 2026-09-28 source [1]

Suspension

5 of 7 filled

Fork: WP XACT 5543 (air fork); Verified, read off the manual page: Manual p. 125 · checked 2026-09-28 source [1]
Fork travel: 278 mm (10.94 in); Verified, read off the manual page: Manual p. 125 · checked 2026-09-28 source [1]
Shock travel: 289 mm (11.38 in); Verified, read off the manual page: Manual p. 125 · checked 2026-09-28 source [1]
Stock fork spring rate: Not yet verified
Stock shock spring rate: Not yet verified
Static sag, bike only: 30 mm (1.18 in); Verified, read off the manual page: Manual p. 128 · checked 2026-09-28 source [1]
Race sag, rider on: 100 mm (3.94 in); Verified, read off the manual page: Manual p. 128 · checked 2026-09-28 source [1]

Fluids and capacities

3 of 3 filled

Coolant capacity: 0.8 l (≈ 27.1 fl oz, converted by MotoXSports); Verified, read off the manual page: Manual p. 122 · checked 2026-09-28 source [1]
Premix ratio: 40:1; Verified, read off the manual page: Manual p. 126 · checked 2026-09-28 source [1]
Fuel capacity: 5.4 l (≈ 1.43 gal, converted by MotoXSports); Verified, read off the manual page: Manual p. 126 · checked 2026-09-28 source [1]

Service specs

6 of 6 filled

Gearbox oil: Engine oil (15W/50), Partially synthetic: 0.50 l (0.132 liq. galUS); Verified, read off the manual page: Manual p. 122 · checked 2026-10-16 source [1]
Fork oil: Fork oil (48601166S1) (SAE 4): right outer assembly 363 ±10 ml (12.27 ±0.34 fl. ozUS); left outer assembly 100 ±20 ml (3.38 ±0.68 fl. ozUS); Verified, read off the manual page: Manual p. 127 · checked 2026-10-16 source [1]
Brake fluid: DOT 5.1; Verified, read off the manual page: Manual p. 80 · checked 2026-10-16 source [1]
Coolant type: Coolant; antifreeze protection to at least: −25 °C (−13.0 °F); Verified, read off the manual page: Manual p. 122 · checked 2026-10-16 source [1]
Fuel octane: Super unleaded (98 octane); Verified, read off the manual page: Manual p. 126 · checked 2026-10-16 source [1]
Idle speed: 1,500 rpm … 2,000 rpm (25.00 Hz … 33.33 Hz); Verified, read off the manual page: Manual p. 121 · checked 2026-10-16 source [1]

Maintenance

3 of 3 filled

Tire pressure (off-road): 1.0 bar (14.5 psi) front and rear; Verified, read off the manual page: Manual p. 126 · checked 2026-09-28 source [1]
Chain slack: 43-46 mm (1.69-1.81 in); Verified, read off the manual page: Manual p. 69 · checked 2026-09-28 source [1]
Spark plug and gap: BRISK AR10C, gap 0.70 mm; Verified, read off the manual page: Manual p. 121 · checked 2026-09-28 source [1]

Dimensions

3 of 3 filled

Seat height: 845 mm (≈ 33.3 in, converted by MotoXSports); Verified, read off the manual page: Manual p. 125 · checked 2026-09-28 source [1]
Wheelbase: 1282 mm (≈ 50.5 in, converted by MotoXSports); Verified, read off the manual page: Manual p. 125 · checked 2026-09-28 source [1]
Weight (weight without fuel approx.): 68 kg (≈ 150 lb, converted by MotoXSports); Verified, read off the manual page: Manual p. 126 · checked 2026-09-28 source [1]

Solid marks are owner's-manual pages; hollow marks are manufacturer web or spec-sheet figures still waiting on a manual page. Last reviewed 2026-10-16. 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 428 Owner's manual p. 125428 chains at MotoSport 428 master links at MotoSport
Sprockets: Stock front sprocket 13T Owner's manual p. 125Stock rear sprocket 46T Owner's manual p. 12513T front sprockets at MotoSport 46T rear sprockets at MotoSport
Tires: Front tire 70/100-17 M/C 40M TT Owner's manual p. 126Rear tire 90/100-14 M/C 49M TT Owner's manual p. 126Front tires 70/100-17 at MotoSport Tubes 70/100-17 at MotoSport Rear tires 90/100-14 at MotoSport Tubes 90/100-14 at MotoSport
Coolant: Coolant capacity 800 ml (27.1 fl oz) Owner's manual p. 122Coolant 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 70/100-17

Rear tire, stock size 90/100-14

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.

3 part specs not yet verified; see data coverage.

Use this bike

Tools for this bike

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Service schedule

47 rows from the owner's manual schedule, pp. 32-33, counted in hours, at these intervals:

After one operating hour
Every 15 operating hours
Every 45 operating hours
Every 90 operating hours
Every 24 months

Check what's due or track it in My Bike. Buying one used? The hours check lists what the schedule calls for by its meter reading.

Riding

Where kids can ride: tracks and areas whose own pages mention young riders.

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

25 of 30 fields read off a manual page.

Not yet verified (5): chain links, front rim, rear rim, fork spring rate, shock spring rate.

See coverage for every bike

Sources

1
KTM Owner's Manual 2027 85 SX, Item no. 3240375en (12/08/2026); owner-supplied copy from the KTM Group print-on-demand portalpp. 69, 80, 121, 122, 125, 126, 127, 128Manual page, verified. Covers stock front sprocket, stock rear sprocket, chain pitch, front tire, rear tire, fork, fork travel, shock travel, static sag, bike only, race sag, rider on, coolant capacity, fuel capacity, premix ratio, tire pressure (off-road), chain slack, spark plug and gap, seat height, wheelbase, weight (weight without fuel approx.), weight, as labelled, gearbox oil, fork oil, brake fluid, coolant type, fuel octane, idle speed; checked 2026-10-16.

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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