Yamaha YZ / IT (premix) — Example photo: Goygoo, CC BY-SA 3.0, Wikimedia Commons

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Yamaha · Two-stroke single, premix, chain drive

YZ / IT (premix)

Library entry covers 1974-2026

62 factory 44 guideline

Published source

Yamaha YZ125T1 Owner's Service Manual (Yamaha Motor Co., 2004)

Factory workshop manual. Covers 2005 (YZ125T1; manual printed 2004).

106 items for a 1986 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: Magneto (incl. magdyno, flywheel magneto)
Charging: Alternator / stator with rectifier
Battery: Wet cell (flooded lead-acid, needs topping up)
Fuel system: Single carburetor
Cooling: Air / oil 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, twin shocks
Front brake: Drum (or band / stirrup)
Rear brake: Drum (or band / belt rim)
Wheels: Spoked, tubed
Sidecar: No sidecar

Maintenance schedule

1986 Yamaha YZ / IT (premix)

On the road: every 200 km

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 500 km

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 1,000 km

1 item

Check chain slack and rear wheel alignment

Pre-ride / on the road

Guideline

On the road: no interval set

1 item

Lubricate drive chain

Pre-ride / on the road

Factory

Manual: Drive chain: lubricate, slack, alignment. Factory: Maintenance intervals p.3-1: after break-in and every race

Every 1,600 km or 1 month

1 item

Check battery electrolyte, top up with distilled water

Ignition and electrics

Guideline

Wet-cell batteries on old machines need regular topping up, more in hot weather.

Every 1,600 km or 6 months

3 items

Adjust front drum brake

Brakes

Guideline
Adjust rear drum brake and rod / cable linkage

Brakes

Guideline
Inspect tire tread, sidewalls and date codes

Wheels and tires

Guideline

Every 3,000 km or 12 months

1 item

Replace spark plugs (two-stroke)

Engine

Guideline

Every 5,000 km or 12 months

10 items

Check throttle cable(s) free play and return

Fuel and air

Guideline
Check / set ignition timing

Ignition and electrics

Guideline
Clean and gap contact breaker points, oil cam felt

Ignition and electrics

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
Check steering head bearing adjustment

Front end

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 spoke tension and wheel true

Wheels and tires

Guideline

Every 6,500 km or 12 months

2 items

Adjust clutch free play, lubricate cable and lever pivot

Primary and gearbox

Guideline
Lubricate brake cam spindles, check linings and drums

Brakes

Guideline

Every 9,500 km or 12 months

4 items

Check charging voltage and regulator / cut-out

Ignition and electrics

Guideline
Check swingarm bushes for play

Rear suspension and frame

Guideline
Inspect rear shocks for leaks and damping

Rear suspension and frame

Guideline
Lubricate speedometer / tachometer cables, check drive

Controls and cables

Guideline

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

Every 9,500 km or 2 years

2 items

Lubricate and check automatic advance unit

Ignition and electrics

Guideline
Magneto: clean slip ring and pickup brush, check HT lead

Ignition and electrics

Guideline

Every 13,000 km or 2 years

1 item

Replace spark plugs

Engine

Guideline

Every 16,000 km or 2 years

1 item

Compression test (or leak-down)

Engine

Guideline

Every 19,500 km or 2 years

1 item

Replace air filter element

Fuel and air

Guideline

Every 19,500 km or 3 years

1 item

Replace points and condenser

Ignition and electrics

Guideline

Every 24,000 km

1 item

Replace brake linings / skim drums (wear based)

Brakes

Guideline

Every 29,000 km

1 item

Replace chain and sprockets (wear based)

Final drive

Guideline

Every 32,000 km or 4 years

1 item

Repack / replace wheel bearings

Wheels and tires

Guideline

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

Every 40,000 km or 6 years

1 item

Replace swingarm bushes / bearings

Rear suspension and frame

Guideline

Every 40,000 km or 10 years

1 item

Magneto overhaul / re-magnetize, replace capacitor

Ignition and electrics

Guideline

Weak spark when hot is the classic symptom. Old capacitors fail with age, not miles.

Every 48,500 km or 6 years

1 item

Rebuild forks: seals, bushes, springs

Front end

Guideline

Every 6 months

1 item

Clean battery terminals, check charge and strap

Ignition and electrics

Guideline

Every 12 months

2 items

Replace brake fluid

Brakes

Factory

Manual: Brakes: replace brake fluid. Factory: Maintenance intervals p.3-2: every one year
Check speedometer / odometer against a known distance

Controls and cables

Guideline

Old speedos drift with tire size and drive wear. Use phone GPS over a measured 10 miles / km.

Every 2 years

3 items

Replace coolant

Engine

Factory

Manual: Cooling system: replace coolant. Factory: Maintenance intervals p.3-2: 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

1 item

Replace fuel lines

Fuel and air

Guideline

Old rubber and modern ethanol fuel do not mix well.

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

59 items

COOLING SYSTEM: Check coolant level and leakage

Engine

Factory

Factory: As printed: After break-in; Every race
COOLING SYSTEM: Check radiator cap operation

Engine

Factory

Factory: As printed: As required
COOLING SYSTEM: Inspect hoses

Engine

Factory

Factory: As printed: Every race
CRANK: Inspect and clean

Engine

Factory

Factory: As printed: Every fifth; As required
CYLINDER HEAD: Retighten

Engine

Factory

Factory: As printed: After break-in; Every race; Remarks: Check gasket
CYLINDER: Inspect and clean

Engine

Factory

Factory: As printed: After break-in; Every race; Remarks: Inspect score marks, Inspect wear
CYLINDER: Replace

Engine

Factory

Factory: As printed: As required
Decarbonize exhaust ports, pipes and baffles

Engine

Factory

Manual: Cylinder head and YPVS: inspect and clean carbon deposits. Factory: Maintenance intervals p.3-1: after break-in and every race
Inspect, clean and gap spark plugs

Engine

Factory

Manual: Spark plug: inspect and clean. Factory: Maintenance intervals p.3-1: after break-in and every race; replace as required
MUFFLER: Clean

Engine

Factory

Factory: As printed: Every fifth
MUFFLER: Inspect

Engine

Factory

Factory: As printed: After break-in; Every race
MUFFLER: Retighten

Engine

Factory

Factory: As printed: After break-in; Every race
OUTSIDE NUTS AND BOLTS: Retighten

Engine

Factory

Factory: As printed: After break-in; Every race; Remarks: Refer to "STARTING AND BREAK-IN" section in the CHAPTER 1.
PISTON PIN, SMALL END BEARING: Inspect

Engine

Factory

Factory: As printed: Every race
PISTON PIN, SMALL END BEARING: Replace

Engine

Factory

Factory: As printed: As required
PISTON RING: Inspect

Engine

Factory

Factory: As printed: After break-in; Every race; Remarks: Check ring end gap
PISTON: Inspect and clean

Engine

Factory

Factory: As printed: After break-in; Every race; Remarks: Inspect crack, Inspect carbon deposits and eliminate them
PROTECTOR GUIDE: Replace

Engine

Factory

Factory: As printed: As required
Piston ring: replace

Engine

Factory

Factory: Maintenance intervals p.3-1: every third race or as required
Piston: replace

Engine

Factory

Factory: Maintenance intervals p.3-1: every fifth race or as required; inspect every race
ROTOR NUT: Retighten

Engine

Factory

Factory: As printed: After break-in; Every fifth
SPARK PLUG: Replace

Engine

Factory

Factory: As printed: As required
AIR FILTER: Replace

Fuel and air

Factory

Factory: As printed: As required
Clean / inspect air filter

Fuel and air

Factory

Manual: Air filter: clean and lubricate. Factory: Maintenance intervals p.3-2: after break-in and every race
Clean carburetor float bowl(s), check float level and jets

Fuel and air

Factory

Manual: Carburetor: inspect, adjust and clean. Factory: Maintenance intervals p.3-1: after break-in and every race
Clean fuel tap filter / sediment bowl

Fuel and air

Factory

Manual: Fuel tank, cock: clean and inspect. Factory: Maintenance intervals p.3-2: after break-in, then every third race
CLUTCH: Inspect and adjust

Primary and gearbox

Factory

Factory: As printed: After break-in; Every race; Remarks: Inspect housing, friction plate, clutch plate and spring
CLUTCH: Replace

Primary and gearbox

Factory

Factory: As printed: As required
Change gearbox oil

Primary and gearbox

Factory

Manual: Transmission: replace oil. Factory: Maintenance intervals p.3-1: after break-in, then every fifth race
TRANSMISSION: Inspect

Primary and gearbox

Factory

Factory: As printed: As required
TRANSMISSION: Replace bearing

Primary and gearbox

Factory

Factory: As printed: As required
CHAIN GUARD AND ROLLERS: Inspect

Final drive

Factory

Factory: As printed: After break-in; Every race
DRIVE CHAIN: Replace

Final drive

Factory

Factory: As printed: As required
Change fork oil

Front end

Factory

Manual: Front forks: replace oil. Factory: Maintenance intervals p.3-2: after break-in, then every fifth race
FRONT FORK OIL SEAL AND DUST SEAL: Clean and lube

Front end

Factory

Factory: As printed: After break-in; Every race; Remarks: Lithium base grease
FRONT FORKS: Inspect and adjust

Front end

Factory

Factory: As printed: After break-in; Every race
FRONT FORKS: Replace oil seal

Front end

Factory

Factory: As printed: As required
Repack / replace steering head bearings

Front end

Factory

Manual: Steering head: clean and lube. Factory: Maintenance intervals p.3-2: every fifth race; replace bearing as required
SHIFT FORK, SHIFT CAM, GUIDE BAR: Inspect

Front end

Factory

Factory: As printed: As required; Remarks: Inspect wear
STEERING HEAD: Inspect free play and retighten

Front end

Factory

Factory: As printed: After break-in; Every race
STEERING HEAD: Replace bearing

Front end

Factory

Factory: As printed: As required
Clean and grease rear suspension linkage

Rear suspension and frame

Factory

Manual: Relay arm, connecting rod: inspect, lube and retighten. Factory: Maintenance intervals p.3-2: after break-in and every race
FRAME: Clean and inspect

Rear suspension and frame

Factory

Factory: As printed: After break-in; Every race
Grease swingarm pivot

Rear suspension and frame

Factory

Manual: Swingarm: inspect, lube and retighten. Factory: Maintenance intervals p.3-2: after break-in and every race
REAR SHOCK ABSORBER: Inspect and adjust

Rear suspension and frame

Factory

Factory: As printed: After break-in; Every race
REAR SHOCK ABSORBER: Lube

Rear suspension and frame

Factory

Factory: As printed: Every third; As required (After rain ride); Remarks: Molybdenum disulfide grease
REAR SHOCK ABSORBER: Retighten

Rear suspension and frame

Factory

Factory: As printed: After break-in; Every race
BRAKES: Adjust lever position and pedal height

Brakes

Factory

Factory: As printed: After break-in; Every race
BRAKES: Check brake disc surface

Brakes

Factory

Factory: As printed: After break-in; Every race
BRAKES: Check fluid level and leakage

Brakes

Factory

Factory: As printed: After break-in; Every race
BRAKES: Lubricate pivot point

Brakes

Factory

Factory: As printed: After break-in; Every race
BRAKES: Replace pads

Brakes

Factory

Factory: As printed: As required
BRAKES: Retighten brake disc bolts, caliper bolts, master cylinder bolts and union bolts

Brakes

Factory

Factory: As printed: After break-in; Every race
Check wheel bearings for play

Wheels and tires

Factory

Manual: Tire, wheels: inspect bearings, lubricate. Factory: Maintenance intervals p.3-2: every third race; replace bearings as required
TIRE, WHEELS: Inspect air pressure, wheel run-out, tire wear and spoke looseness

Wheels and tires

Factory

Factory: As printed: After break-in; Every race
TIRE, WHEELS: Replace bearings

Wheels and tires

Factory

Factory: As printed: As required
TIRE, WHEELS: Retighten sprocket bolt

Wheels and tires

Factory

Factory: As printed: After break-in; Every race
Lubricate control cables and lever pivots

Controls and cables

Factory

Manual: Throttle, control cable: lubricate. Factory: Maintenance intervals p.3-2: after break-in and every race
THROTTLE, CONTROL CABLE: Check routing and connection

Controls and cables

Factory

Factory: As printed: After break-in; Every race

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.