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Yamaha · Two-stroke single, premix, chain drive

YZ 125

Library entry covers 2002-2025

66 factory 34 guideline

Published source

Yamaha YZ125(D) Owner's Service Manual, Maintenance intervals pp.3-1 to 3-4 (ManualsLib pages 44-47)

Factory service manual. Covers YZ125(D), the 2013 model; chart columns are races, with the hours printed in the headers; read from the rendered pages.

100 items for a 2012 model, grouped by interval the way a factory chart is laid out.

How this bike is built (what the schedule is based on)

Engine cycle: Two-stroke
Engine lubrication: Two-stroke premix (oil in fuel)
Oil filtration: None (no filter)
Valve gear: None (two-stroke porting)
Ignition: Electronic (CDI / transistor / ECU)
Charging: Alternator / stator with rectifier
Battery: Wet cell (flooded lead-acid, needs topping up)
Fuel system: Single carburetor
Cooling: Liquid cooled
Primary drive: Gear or chain inside engine, shares engine oil
Gearbox oil: Separate gearbox oil
Clutch control: Hand lever, cable
Final drive: Chain
Front suspension: Telescopic fork
Rear suspension: Swingarm, single shock / cantilever
Front brake: Disc, hydraulic
Rear brake: Disc, hydraulic
Wheels: Spoked, tubed
Sidecar: No sidecar

Maintenance schedule

2012 Yamaha YZ 125

On the road: every 150 mi

1 item

Check two-stroke oil tank / carry premix oil

Pre-ride / on the road

Guideline

Running a two-stroke out of oil seizes it. Injection bikes: check the tank. Premix: carry oil and a measure.

On the road: every 300 mi

2 items

Check lights, horn, brake light switches

Pre-ride / on the road

Guideline
Check tire pressures

Pre-ride / on the road

Guideline

On the road: every 500 mi

1 item

Check coolant level

Pre-ride / on the road

Guideline

On the road: every 600 mi

1 item

Check chain slack and rear wheel alignment

Pre-ride / on the road

Guideline

On the road: every 2.5 h

1 item

Lubricate drive chain

Pre-ride / on the road

Factory

Manual: Drive chain: Lubricate, slack, alignment. Factory: Marked every race (about 2.5 hours), and after break-in. Use chain lube. Chain slack 48-58 mm (1.9-2.3 in). Replace as required.

Every 2,000 mi or 12 months

1 item

Replace spark plugs (two-stroke)

Engine

Guideline

Every 3,000 mi or 12 months

8 items

Clean fuel tap filter / sediment bowl

Fuel and air

Guideline
Clean drive chain thoroughly (remove and soak, re-lube)

Final drive

Guideline

Non O-ring chains on old machines: remove, clean, soak in hot chain grease or lube, refit with the master link clip closed end leading.
Inspect chain and sprockets for wear (measure stretch)

Final drive

Guideline
Inspect fork seals, stanchions and fork boots

Front end

Guideline
Check footrests, pegs, rear brake and gear lever pivots

Rear suspension and frame

Guideline
Grease and check center / side stand and springs

Rear suspension and frame

Guideline
Check brake pads and discs

Brakes

Guideline
Check spoke tension and wheel true

Wheels and tires

Guideline

Every 3,000 mi or 2 years

1 item

Decarbonize exhaust ports, pipes and baffles

Engine

Guideline

Two-strokes coke up the exhaust port and muffler baffles; power falls off gradually.

Every 4,000 mi or 12 months

1 item

Adjust clutch free play, lubricate cable and lever pivot

Primary and gearbox

Guideline

Every 6,000 mi or 12 months

5 items

Clean carburetor float bowl(s), check float level and jets

Fuel and air

Guideline

Ethanol fuel varnishes old carbs quickly in storage.
Check charging voltage and regulator / cut-out

Ignition and electrics

Guideline
Check swingarm bushes for play

Rear suspension and frame

Guideline
Lubricate control cables and lever pivots

Controls and cables

Guideline
Lubricate speedometer / tachometer cables, check drive

Controls and cables

Guideline

A dry speedo cable whips the needle and eventually kills the instrument.

Every 10,000 mi or 2 years

1 item

Compression test (or leak-down)

Engine

Guideline

Every 20,000 mi or 4 years

2 items

Repack / replace steering head bearings

Front end

Guideline

Many old machines use loose balls in cups and cones. Taper roller conversions are common.
Repack / replace wheel bearings

Wheels and tires

Guideline

Cup-and-cone and taper roller hubs need periodic repacking and adjustment.

Every 25,000 mi or 6 years

1 item

Replace swingarm bushes / bearings

Rear suspension and frame

Guideline

Every 30,000 mi or 6 years

1 item

Rebuild forks: seals, bushes, springs

Front end

Guideline

Every 2.5 h

33 items

Cooling system: Check coolant level and leakage

Engine

Factory

Factory: Marked every race (about 2.5 hours), and after break-in. Check radiator cap operation as required.
Cylinder head: Inspect and clean

Engine

Factory

Factory: Marked every race (about 2.5 hours), and after break-in. Inspect carbon deposits and eliminate them. Check gasket.
Cylinder head: Retighten

Engine

Factory

Factory: Marked every race (about 2.5 hours), and after break-in.
Cylinder: Inspect and clean

Engine

Factory

Factory: Marked every race (about 2.5 hours), and after break-in. Inspect score marks. Replace as required.
Inspect coolant hoses and clamps

Engine

Factory

Manual: Cooling system: Inspect hoses. Factory: Marked every race (about 2.5 hours).
Muffler: Inspect

Engine

Factory

Factory: Marked every race (about 2.5 hours), and after break-in.
Muffler: Retighten

Engine

Factory

Factory: Marked every race (about 2.5 hours), and after break-in. Replace fiber as required: when the exhaust sound becomes louder or a performance drop is felt.
Outside nuts and bolts: Retighten

Engine

Factory

Factory: Marked every race (about 2.5 hours), and after break-in. Refer to Starting and break-in in chapter 1.
Piston pin, small end bearing: Inspect

Engine

Factory

Factory: Marked every race (about 2.5 hours). Replace as required.
Piston ring: Inspect

Engine

Factory

Factory: Marked every race (about 2.5 hours), and after break-in. Check ring end gap.
Piston: Inspect and clean

Engine

Factory

Factory: Marked every race (about 2.5 hours), and after break-in. Inspect crack.
YPVS: Inspect and clean

Engine

Factory

Factory: Marked every race (about 2.5 hours), and after break-in. Inspect carbon deposits and eliminate them.
Carburetor: Inspect, adjust and clean

Fuel and air

Factory

Factory: Marked every race (about 2.5 hours), and after break-in.
Check throttle cable(s) free play and return

Fuel and air

Factory

Manual: Throttle, control cable: Check routing and connection. Factory: Marked every race (about 2.5 hours), and after break-in.
Clean / inspect air filter

Fuel and air

Factory

Manual: Air filter: Clean and lubricate. Factory: Marked every race (about 2.5 hours), and after break-in. Use foam air-filter oil or equivalent oil. Replace as required.
Clutch: Inspect and adjust

Primary and gearbox

Factory

Factory: Marked every race (about 2.5 hours), and after break-in. Inspect housing, friction plate, clutch plate and spring. Replace as required.
Drive chain guide and rollers: Inspect

Final drive

Factory

Factory: Marked every race (about 2.5 hours), and after break-in.
Check steering head bearing adjustment

Front end

Factory

Manual: Steering head: Inspect free play and retighten. Factory: Marked every race (about 2.5 hours), and after break-in.
Front fork oil seal and dust seal: Clean and lube

Front end

Factory

Factory: Marked every race (about 2.5 hours), and after break-in. Lithium base grease.
Front forks: Inspect and adjust

Front end

Factory

Factory: Marked every race (about 2.5 hours), and after break-in.
Clean and grease rear suspension linkage

Rear suspension and frame

Factory

Manual: Relay arm, connecting rod: Inspect, lube and retighten. Factory: Marked every race (about 2.5 hours), and after break-in. Molybdenum disulfide grease.
Frame: Clean and inspect

Rear suspension and frame

Factory

Factory: Marked every race (about 2.5 hours), and after break-in.
Grease swingarm pivot

Rear suspension and frame

Factory

Manual: Swingarm: Inspect, lube and retighten. Factory: Marked every race (about 2.5 hours), and after break-in. Molybdenum disulfide grease.
Inspect rear shocks for leaks and damping

Rear suspension and frame

Factory

Manual: Rear shock absorber: Inspect and adjust. Factory: Marked every race (about 2.5 hours), and after break-in.
Rear shock absorber: Retighten

Rear suspension and frame

Factory

Factory: Marked every race (about 2.5 hours), and after break-in.
Brakes: Adjust lever position and pedal height

Brakes

Factory

Factory: Marked every race (about 2.5 hours), and after break-in.
Brakes: Check brake disc surface

Brakes

Factory

Factory: Marked every race (about 2.5 hours), and after break-in.
Brakes: Check fluid level and leakage

Brakes

Factory

Factory: Marked every race (about 2.5 hours), and after break-in.
Brakes: Lubricate pivot point

Brakes

Factory

Factory: Marked every race (about 2.5 hours), and after break-in.
Brakes: Retighten brake disc bolts, caliper bolts, master cylinder bolts and union bolts

Brakes

Factory

Factory: Marked every race (about 2.5 hours), and after break-in. Replace pads as required.
Inspect tire tread, sidewalls and date codes

Wheels and tires

Factory

Manual: Tire, wheels: Inspect air pressure, wheel run-out, tire wear and spoke looseness. Factory: Marked every race (about 2.5 hours), and after break-in.
Tire, wheels: Retighten sprocket bolt

Wheels and tires

Factory

Factory: Marked every race (about 2.5 hours), and after break-in.
Throttle, control cable: Lubricate

Controls and cables

Factory

Factory: Marked every race (about 2.5 hours), and after break-in. Yamaha cable lube or SAE 10W-40 motor oil.

Every 7.5 h

6 items

Inspect, clean and gap spark plugs

Engine

Factory

Manual: Spark plug: Inspect and clean. Factory: Marked every third race (about 7.5 hours), and after break-in. Replace as required.
Piston ring: Replace

Engine

Factory

Factory: Marked every third race (about 7.5 hours). Also as required.
Fuel tank, cock: Clean and inspect

Fuel and air

Factory

Factory: Marked every third race (about 7.5 hours), and after break-in.
Rear shock absorber: Lube

Rear suspension and frame

Factory

Factory: Marked every third race (about 7.5 hours). Also as required (after rain ride). Molybdenum disulfide grease.
Check wheel bearings for play

Wheels and tires

Factory

Manual: Tire, wheels: Inspect bearings. Factory: Marked every third race (about 7.5 hours). Replace bearings as required.
Tire, wheels: Lubricate

Wheels and tires

Factory

Factory: Marked every third race (about 7.5 hours). Lithium base grease.

Every 12.5 h

7 items

Crank: Inspect and clean

Engine

Factory

Factory: Marked every fifth race (about 12.5 hours). Also as required.
Muffler: Clean

Engine

Factory

Factory: Marked every fifth race (about 12.5 hours).
Piston: Replace

Engine

Factory

Factory: Marked every fifth race (about 12.5 hours). Also as required. Inspect carbon deposits and eliminate them.
Rotor nut: Retighten

Engine

Factory

Factory: Marked every fifth race (about 12.5 hours), and after break-in.
Change gearbox oil

Primary and gearbox

Factory

Manual: Transmission: Replace oil. Factory: Marked every fifth race (about 12.5 hours), and after break-in. Yamalube SAE 10W-40, API SG or higher, JASO MA. Inspect and replace bearing as required.
Change fork oil

Front end

Factory

Manual: Front forks: Replace oil. Factory: Marked every fifth race (about 12.5 hours), and after break-in. Suspension oil S1. Replace oil seal as required.
Steering head: Clean and lube

Front end

Factory

Factory: Marked every fifth race (about 12.5 hours). Lithium base grease. Replace bearing as required.

Every 6 months

1 item

Clean battery terminals, check charge and strap

Ignition and electrics

Guideline

Every 12 months

2 items

Rear shock absorber: Replace spring seat

Rear suspension and frame

Factory

Factory: As required; remarks: every one year.
Replace brake fluid

Brakes

Factory

Manual: Brakes: Replace brake fluid. Factory: As required; remarks: every one year.

Every 2 years

3 items

Replace coolant

Engine

Factory

Manual: Cooling system: Replace coolant. Factory: As required; remarks: every two years.
Inspect wiring, bullet connectors and ground points

Ignition and electrics

Guideline
Inspect frame, welds and lugs for cracks

Rear suspension and frame

Guideline

Every 4 years

3 items

Replace fuel lines

Fuel and air

Guideline

Old rubber and modern ethanol fuel do not mix well.
Inspect brake hoses; replace old rubber

Brakes

Guideline
Rebuild calipers and master cylinders (seals)

Brakes

Guideline

Every 6 years

2 items

Replace inner tubes and rim tape with tires

Wheels and tires

Guideline
Replace tires on age (regardless of tread)

Wheels and tires

Guideline

No interval set

16 items

Cooling system: Check radiator cap operation

Engine

Factory

Factory: Marked as required (no set interval).
Cylinder: Replace

Engine

Factory

Factory: Marked as required (no set interval).
Muffler: Replace fiber

Engine

Factory

Factory: Marked as required (no set interval).
Piston pin, small end bearing: Replace

Engine

Factory

Factory: Marked as required (no set interval).
Protector guide: Replace

Engine

Factory

Factory: Marked as required (no set interval).
Replace spark plugs

Engine

Factory

Manual: Spark plug: Replace. Factory: Marked as required (no set interval).
Replace air filter element

Fuel and air

Factory

Manual: Air filter: Replace. Factory: Marked as required (no set interval).
Clutch: Replace

Primary and gearbox

Factory

Factory: Marked as required (no set interval).
Transmission: Inspect

Primary and gearbox

Factory

Factory: Marked as required (no set interval).
Transmission: Replace bearing

Primary and gearbox

Factory

Factory: Marked as required (no set interval).
Replace chain and sprockets (wear based)

Final drive

Factory

Manual: Drive chain: Replace. Factory: Marked as required (no set interval).
Front forks: Replace oil seal

Front end

Factory

Factory: Marked as required (no set interval).
Shift fork, shift cam, guide bar: Inspect

Front end

Factory

Factory: Marked as required (no set interval).
Steering head: Replace bearing

Front end

Factory

Factory: Marked as required (no set interval).
Brakes: Replace pads

Brakes

Factory

Factory: Marked as required (no set interval).
Tire, wheels: Replace bearings

Wheels and tires

Factory

Factory: Marked as required (no set interval).

Guideline lines: Intervals here are general guidelines for the machine's era and layout, compiled for this app. They are not factory manual figures. Check your workshop manual, and edit any interval in the bike's Schedule tab.