The Garage

Motocross

Stock-size parts in stock at MotoSport

Yamaha YZ125 2016

Motocross, 125cc 2T

Verified

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

From the owner’s manual: coolant 0.90 L, p. 2-1; front tire 80/100-21 51M, p. 2-2; rear tire 100/90-19 57M, p. 2-2. Checked 16 Oct 2026.

No CPSC recall found for the 2016 Yamaha YZ125, 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. 2-2 · checked 2026-09-25 source [1]
Stock rear sprocket
48T
Verified, read off the manual page: Manual p. 2-2 · checked 2026-09-25 source [1]
Chain pitch
520
Verified, read off the manual page: Manual p. 2-7 · checked 2026-09-25 source [1]
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. 2-2

Wheels and tires

2 of 4 filled

Front rim
Not yet verified
Rear rim
Not yet verified
Front tire
80/100-21 51M
Verified, read off the manual page: Manual p. 2-2 · checked 2026-09-25 source [1]
Rear tire
100/90-19 57M
Verified, read off the manual page: Manual p. 2-2 · checked 2026-09-25 source [1]

Suspension

2 of 7 filled

Fork
Not yet verified
Fork travel
300 mm (11.8 in)
Verified, read off the manual page: Manual p. 2-2 · checked 2026-09-25 source [1]
Shock travel
315 mm (12.4 in)
Verified, read off the manual page: Manual p. 2-2 · checked 2026-09-25 source [1]
Stock fork spring rate
Not yet verified
Stock shock spring rate
Not yet verified
Static sag, bike only
Not yet verified
Race sag, rider on
Not yet verified

Fluids and capacities

2 of 3 filled

Coolant capacity
0.90 L (≈ 30.4 fl oz, converted by MotoXSports)
Verified, read off the manual page: Manual p. 2-1 · checked 2026-09-25 source [1]
Premix ratio
Not yet verified
Fuel capacity
8.0 L (2.1 US gal)
Verified, read off the manual page: Manual p. 2-1 · checked 2026-09-25 source [1]

Service specs

5 of 6 filled

Gearbox oil
Recommended brand: YAMALUBE SAE10W-40 API service SG type or higher, JASO standard MA; Periodic oil change 0.66 L (0.58 Imp qt, 0.70 US qt); Total amount 0.70 L (0.62 Imp qt, 0.74 US qt)
Verified, read off the manual page: Manual p. 2-1 · checked 2026-10-16 source [1]
Fork oil
Oil capacity 510.0 cm3 (17.99 Imp oz, 17.24 US oz); Oil grade Suspension oil "S1"
Verified, read off the manual page: Manual p. 2-6 · checked 2026-10-16 source [1]
Brake fluid
DOT #4
Verified, read off the manual page: Manual p. 2-7 · checked 2026-10-16 source [1]
Coolant type
High quality ethylene glycol antifreeze containing anti-corrosion for aluminum engine
Verified, read off the manual page: Manual p. 3-6 · checked 2026-10-16 source [1]
Fuel octane
Premium unleaded gasoline only with a research octane number of 95 or higher
Verified, read off the manual page: Manual p. 2-1 · checked 2026-10-16 source [1]
Idle speed
Not yet verified

Maintenance

2 of 3 filled

Tire pressure (off-road)
100 kPa (15 psi) front and rear
Verified, read off the manual page: Manual p. 2-2 · checked 2026-09-25 source [1]
Chain slack
Not yet verified
Spark plug and gap
NGK BR9EVX, gap 0.6-0.7 mm
Verified, read off the manual page: Manual p. 2-1 · checked 2026-09-25 source [1]

Dimensions

3 of 3 filled

Seat height
975 mm (38.4 in)
Verified, read off the manual page: Manual p. 2-1 · checked 2026-09-25 source [1]
Wheelbase
1,445 mm (56.9 in)
Verified, read off the manual page: Manual p. 2-1 · checked 2026-09-25 source [1]
Weight (curb weight)
94 kg (207 lb)
Verified, read off the manual page: Manual p. 2-1 · checked 2026-09-25 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 520 Owner's manual p. 2-7520 chains at MotoSport520 master links at MotoSport
Sprockets
Stock front sprocket 13T Owner's manual p. 2-2Stock rear sprocket 48T Owner's manual p. 2-213T front sprockets at MotoSport48T rear sprockets at MotoSport
Tires
Front tire 80/100-21 51M Owner's manual p. 2-2Rear tire 100/90-19 57M Owner's manual p. 2-2Front tires 80/100-21 at MotoSportTubes 80/100-21 at MotoSportRear tires 100/90-19 at MotoSportTubes 100/90-19 at MotoSport
Coolant
Coolant capacity 900 ml (30.4 fl oz) Owner's manual p. 2-1Coolant 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.

3 part specs not yet verified; see data coverage.

Tools for this bike

Compare with

Comparisons with other bikes use the newest model year on file: Yamaha YZ125 2027.

Other model years

All 4 model years, 2016 to 2027, side by side

Service schedule

65 rows from the owner's manual schedule, pp. 3-1 to 3-4, counted in races, at these intervals:

  • After break-in
  • Every race
  • Every third
  • Every fifth
  • As required

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.

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.

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
Setup B — what you are thinking about
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

19 of 30 fields read off a manual page.

Not yet verified (11): chain links, front rim, rear rim, fork, fork spring rate, shock spring rate, static sag, race sag, premix ratio, chain slack, idle speed.

See coverage for every bike

Sources

  1. 1
    Yamaha 2016 YZ125 / YZ125G2 Owner's Manual (multilingual edition); owner-supplied copypp. 2-1, 2-2, 2-6, 2-7, 3-6Manual page, verified. Covers stock front sprocket, stock rear sprocket, chain pitch, front tire, rear tire, fork travel, shock travel, coolant capacity, fuel capacity, seat height, wheelbase, weight (curb weight), tire pressure (off-road), spark plug and gap, weight, as labelled, gearbox oil, fork oil, brake fluid, coolant type, fuel octane; 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
All bikes