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Junak · Overhead-cam four-stroke single, wet sump, gearbox shares engine oil, chain drive

121 FL

Library entry covers 2020

19 factory 46 guideline

Published source

Junak RZ125 / Racer / 121 FL / 125 S instrukcja obslugi, section 13 Harmonogram przegladow serwisowych p.22

Factory owner's handbook. Covers Junak owner's manual covering the RZ 125, Racer, 121 FL and 125 S (Polish; junak.com.pl file uploaded November 2025).

65 items for a 2020 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: Four-stroke
Engine lubrication: Wet sump (oil in crankcase)
Oil filtration: Replaceable cartridge or spin-on filter
Valve gear: Overhead cam, screw/locknut adjusters
Ignition: Electronic (CDI / transistor / ECU)
Charging: Alternator / stator with rectifier
Battery: Wet cell (flooded lead-acid, needs topping up)
Fuel system: Fuel injection
Cooling: Air / oil cooled
Primary drive: Gear or chain inside engine, shares engine oil
Gearbox oil: Shares engine oil
Clutch control: Hand lever, cable
Final drive: Chain
Front suspension: Telescopic fork
Rear suspension: Swingarm, twin shocks
Front brake: Disc, hydraulic
Rear brake: Disc, hydraulic
Wheels: Cast / alloy, tubeless
Sidecar: No sidecar

Maintenance schedule

2020 Junak 121 FL

On the road: every 200 mi

1 item

Check engine oil level

Pre-ride / on the road

Guideline

Each fuel stop on old machines. Dry sump: check the tank hot, engine idling or just stopped, per your manual.

On the road: every 300 mi

3 items

Check lights, horn, brake light switches

Pre-ride / on the road

Guideline
Check tire pressures

Pre-ride / on the road

Guideline
Lubricate drive chain

Pre-ride / on the road

Guideline

Lube warm, ideally at the end of the riding day so it soaks in overnight. Sooner after rain.

On the road: every 600 mi

1 item

Check chain slack and rear wheel alignment

Pre-ride / on the road

Guideline

Every 190 mi

1 item

Drive chain (lubricate)

Final drive

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22), drive chain and sprockets row: lubricate every 300 km. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.

Every 1,000 mi or 6 months

1 item

Inspect tire tread, sidewalls and date codes

Wheels and tires

Guideline

Every 1,900 mi or 12 months

12 items

Bolts and nuts of every part (tighten)

Engine

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22) row "Sruby i nakretki kazdej czesci": D at 300 km (12 months), 3,000 km, 6,000 km, 9,000 km, 12,000 km. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.
Engine oil (replace)

Engine

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22) row "Olej silnikowy": W at 300 km (12 months), 1,500 km, 3,000 km, 6,000 km, 9,000 km, 12,000 km. Row text: replace per the schedule or once a year. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.
Spark plug (replace)

Engine

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22) row "Swieca": W at 3,000 km, 6,000 km, 9,000 km, 12,000 km. Also R at 300 km (12 months); R at 1,500 km. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.
Valve clearance (check)

Engine

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22) row "Luzy zaworowe": S at 300 km (12 months), 1,500 km, 3,000 km, 6,000 km, 9,000 km, 12,000 km. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.
Air filter (check, clean or replace)

Fuel and air

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22) row "Filtr powietrza": S at 300 km (12 months), 1,500 km, 3,000 km, 6,000 km, 9,000 km, 12,000 km. Starred: with frequent use in dusty conditions, clean or replace the air filter elements more often. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.
Fuel pump/fuel injection system (check)

Fuel and air

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22) row "Pompa paliwa/uklad wtrysku paliwa": S at 300 km (12 months), 1,500 km, 3,000 km, 6,000 km, 9,000 km, 12,000 km. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.
Battery electrolyte (check)

Ignition and electrics

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22) row "Elektrolit w akumulatorze": S at 1,500 km, 3,000 km, 6,000 km, 9,000 km, 12,000 km. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.
Clutch (check)

Primary and gearbox

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22) row "Sprzeglo": S at 3,000 km, 6,000 km, 9,000 km, 12,000 km. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.
Drive chain and sprockets (check)

Final drive

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22) row "Lancuch napedowy i zebatki": S at 300 km (12 months), 1,500 km, 3,000 km, 6,000 km, 9,000 km, 12,000 km. Row text: lubricate every 300 km. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.
Wheel and steering bearings (check)

Front end

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22) row "Lozyska kol i ukladu kierowniczego": S at 300 km (12 months), 1,500 km, 3,000 km, 6,000 km, 9,000 km, 12,000 km. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.
Brake fluid (check)

Brakes

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22) row "Plyn hamulcowy": S at 300 km (12 months), 1,500 km, 3,000 km, 6,000 km, 9,000 km. Also W at 12,000 km. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.
Brake system, pads and brake lines (check)

Brakes

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22) row "Uklad hamulcowy (klocki i przewody hamulcowe)": S at 1,500 km, 3,000 km, 6,000 km, 9,000 km, 12,000 km. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.

Every 3,000 mi or 12 months

9 items

Check throttle cable(s) free play and return

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
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 brake pads and discs

Brakes

Guideline
Check wheel bearings for play

Wheels and tires

Guideline

Every 3,700 mi

3 items

Oil screen filter (clean)

Engine

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22) row "Filtr siatkowy oleju": C at 1,500 km, 6,000 km, 12,000 km. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.
Fuel screen filter (check)

Fuel and air

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22) row "Filtr siatkowy paliwa": S at 6,000 km, 12,000 km. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.
Timing chain (adjust)

Final drive

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22) row "Lancuch rozrzadu": R at 1,500 km, 6,000 km, 12,000 km. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.

Every 4,000 mi or 12 months

2 items

Inspect, clean and gap spark plugs

Engine

Guideline
Adjust clutch free play, lubricate cable and lever pivot

Primary and gearbox

Guideline

Every 5,000 mi or 12 months

2 items

Change engine oil

Engine

Guideline

Pre-1970 machines: many owners run non-detergent or classic-spec oil with no filter, so short intervals matter. Dry sump: drain the tank and the crankcase/sump, flush the tank and clean the feed and return screens.
Replace oil filter

Engine

Guideline

Every 6,000 mi or 12 months

6 items

Clean / inspect air filter

Fuel and air

Guideline

Mesh or oiled foam: clean and re-oil. Paper: blow out or replace. Some very early machines have no filter at all.
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 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 7,500 mi or 2 years

1 item

Brake fluid (replace)

Brakes

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22) row "Plyn hamulcowy": W at 12,000 km. Also S at 300 km (12 months); S at 1,500 km; S at 3,000 km; S at 6,000 km; S at 9,000 km. Row text: replace per the schedule or every 2 years. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.

Every 8,000 mi or 2 years

1 item

Check and adjust valve clearances

Engine

Guideline

Every 10,000 mi or 2 years

1 item

Compression test (or leak-down)

Engine

Guideline

Every 12,000 mi or 2 years

3 items

Replace air filter element

Fuel and air

Guideline
Synchronize throttle bodies

Fuel and air

Guideline
Grease swingarm pivot

Rear suspension and frame

Guideline

Every 15,000 mi or 3 years

1 item

Change fork oil

Front end

Guideline

Some early telescopic forks are grease filled or use very small oil quantities. Check your manual.

Every 16,000 mi or 4 years

1 item

Replace spark plugs

Engine

Guideline

Every 18,000 mi

1 item

Replace chain and sprockets (wear based)

Final drive

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 24,000 mi or 4 years

1 item

Replace fuel filter

Fuel and air

Guideline

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 6 months

1 item

Clean battery terminals, check charge and strap

Ignition and electrics

Guideline

Every 2 years

3 items

Inspect wiring, bullet connectors and ground points

Ignition and electrics

Guideline
Inspect frame, welds and lugs for cracks

Rear suspension and frame

Guideline
Replace brake fluid

Brakes

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

1 item

Replace tires on age (regardless of tread)

Wheels and tires

Guideline

No interval set

2 items

Exhaust emission level (check and adjust)

Engine

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22), row "Poziom spalin": regular checking and adjustment (Regularne sprawdzanie i regulacja). Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.
Spark plug (adjust)

Engine

Factory

Factory: Harmonogram przegladow serwisowych (section 13, p.22) row "Swieca": R at 300 km (12 months), 1,500 km. Also W at 3,000 km; W at 6,000 km; W at 9,000 km; W at 12,000 km. Adjusted at 300 and 1,500 km. Legend (translated from Polish): S = check, clean, adjust or replace if necessary; R = adjust; C = clean; W = replace; D = tighten. Footnote: first service after 300 km or 12 months, whichever comes first; later regular services by the indicated km or after 12 months, whichever comes first.

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.