Harley-Davidson EL / FL Knucklehead — Example photo: Triple-green, CC BY-SA 2.0, Wikimedia Commons

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Harley-Davidson · Harley-Davidson Knucklehead (EL/FL 1936-1947)

EL / FL Knucklehead

Library entry covers 1936-1947

66 factory 45 guideline

Published source

Harley-Davidson Service Manual, 1940 to 1947 inclusive: O.H.V. 61/74 and Side Valve 74/80 models (factory)

Factory workshop manual. Covers 1940-1947 (O.H.V. 61 and 74).

111 items for a 1938 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: Dry sump (separate oil tank)
Oil filtration: None (no filter)
Valve gear: Overhead valve, pushrods, adjustable tappets
Ignition: Battery and coil with contact points
Charging: DC generator with regulator
Battery: Wet cell (flooded lead-acid, needs topping up)
Fuel system: Single carburetor
Cooling: Air / oil cooled
Primary drive: Chain fed by engine oil / breather (no separate oil change)
Gearbox oil: Separate gearbox oil
Clutch control: Foot clutch / hand shift
Final drive: Chain
Front suspension: Springer fork
Rear suspension: Rigid (hardtail)
Front brake: Drum (or band / stirrup)
Rear brake: Drum (or band / belt rim)
Wheels: Spoked, tubed
Sidecar: No sidecar

Maintenance schedule

1938 Harley-Davidson EL / FL Knucklehead

On the road: every 300 km

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 500 km

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 800 km

2 items

Grease girder / springer fork links

Pre-ride / on the road

Guideline

Grease gun on every nipple until clean grease shows. Touring days add up fast.
Walk-around: check nuts and bolts for vibration loosening

Pre-ride / on the road

Guideline

Old machines shake things loose: exhaust nuts, mudguard stays, footrests, tank mounts, battery strap.

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: every 1,600 km

1 item

Check road kit: plugs, points file, master link, tube patches, wire, tape

Pre-ride / on the road

Guideline

Every 1,200 km

3 items

Lubricate points marked for 750 mile attention on Lubrication Chart

Ignition and electrics

Factory

Factory: p8-9 chart; reduce to 500 mi wet/muddy/dusty
General Lubrication, SIDECAR: other bearings (brake cross shaft bearings, brake operating shaft) at 750 mile intervals

Brakes

Factory

Factory: As printed: other bearings at 750 mile intervals
Lubricate control cables and lever pivots

Controls and cables

Factory

Manual: Lubricate front wheel brake hand lever and control cable. Factory: p8 item 16: every 750 mi; oil other control joints regularly

Every 1,600 km or 6 months

1 item

Inspect tire tread, sidewalls and date codes

Wheels and tires

Guideline

Every 1,600 km or 12 months

1 item

Grease saddle pivot, check saddle springs / seat post

Rear suspension and frame

Guideline

Every 1,600 km

2 items

Clean / inspect air filter

Fuel and air

Factory

Manual: Wash air cleaner mesh in gasoline/solvent, re-oil. Factory: p10: at least every 1000 mi; p8: also at each oil change; daily if extremely dusty
Check gearbox oil level

Primary and gearbox

Factory

Manual: Check transmission oil level, add if necessary. Factory: p8 item 22: every two weeks or every 1000 mi, whichever first

Every 2,500 km

24 items

Check and adjust valve clearances

Engine

Factory

Manual: Check valve tappets (engine tune-up). Factory: p11 regular interval item 18; first at 1500 mi
Inspect, clean and gap spark plugs

Engine

Factory

Manual: Check spark plugs (engine tune-up). Factory: p11 regular interval item 18
Regular Interval Inspection and Maintenance: 1. Check condition of oil in tank to determine if oil change is needed.

Engine

Factory

Factory: As printed: REGULAR INTERVAL INSPECTION AND MAINTENANCE: at regular intervals not exceeding 1500 miles
Clean carburetor float bowl(s), check float level and jets

Fuel and air

Factory

Manual: Remove carburetor bowl drain plug and flush bowl. Factory: p11 regular interval item 15
Clean fuel tap filter / sediment bowl

Fuel and air

Factory

Manual: Clean and flush gasoline strainer. Factory: p11 regular interval item 14
Regular Interval Inspection and Maintenance: 18. Completely tune up engine, including: ... carburetor adjustment, and cleaning muffler outlet.

Fuel and air

Factory

Factory: As printed: REGULAR INTERVAL INSPECTION AND MAINTENANCE: at regular intervals not exceeding 1500 miles
Regular Interval Inspection and Maintenance: 20. Road test motorcycle to check carburetor adjustment and all-around performance.

Fuel and air

Factory

Factory: As printed: REGULAR INTERVAL INSPECTION AND MAINTENANCE: at regular intervals not exceeding 1500 miles
Regular Interval Inspection and Maintenance: 5. If motorcycle is equipped with air cleaner, inspect and service if needed.

Fuel and air

Factory

Factory: As printed: REGULAR INTERVAL INSPECTION AND MAINTENANCE: at regular intervals not exceeding 1500 miles
Check / set ignition timing

Ignition and electrics

Factory

Manual: Check ignition timing (engine tune-up). Factory: p11 regular interval item 18, not exceeding 1500 mi
Check battery electrolyte, top up with distilled water

Ignition and electrics

Factory

Manual: Check battery solution level, add distilled water. Factory: p11 item 16
Clean and gap contact breaker points, oil cam felt

Ignition and electrics

Factory

Manual: Grease circuit breaker cam; check breaker points. Factory: p8: grease cam every 1000 mi; p11: points checked at each 1500 mi tune-up
Inspect wiring, bullet connectors and ground points

Ignition and electrics

Factory

Manual: Inspect all wiring connections, check switches and lights. Factory: p11 item 17
Regular Interval Inspection and Maintenance: 19. Note that generator and oil pressure signal lights, in switch panel, go out when engine is running above idling speed.

Ignition and electrics

Factory

Factory: As printed: REGULAR INTERVAL INSPECTION AND MAINTENANCE: at regular intervals not exceeding 1500 miles
Adjust foot clutch and hand-shift linkage, lubricate pivots

Primary and gearbox

Factory

Manual: Check clutch and clutch control adjustments. Factory: p11 item 8; gear shifting control first checked 1500 mi
Check / adjust primary chain

Primary and gearbox

Factory

Manual: Adjust chains. Factory: p11 item 6; p12 inspect chain adjustment at least every week, about 1/2 in. free play
Check primary chain oil supply (breather / pump feed)

Primary and gearbox

Factory

Manual: Check front chain lubrication; flush chain oiler passage. Factory: p11 items 6-7; p13 back off oiler screw about every 2000 mi; first check 250 mi
Clean drive chain thoroughly (remove and soak, re-lube)

Final drive

Factory

Manual: Remove rear chain, inspect, clean and lubricate. Factory: p11 item 6; first 750 mi clean and lubricate rear chain
Adjust front drum brake

Brakes

Factory

Manual: Check brakes, readjust controls. Factory: p11 item 9
Adjust rear drum brake and rod / cable linkage

Brakes

Factory

Manual: Check brakes, readjust controls. Factory: p11 item 9
Regular Interval Inspection and Maintenance: 4. Oil all control joints, namely, clutch, gear shifter, brakes, front brake control wire, and spark and throttle control wires at ends of their respective housings.

Brakes

Factory

Factory: As printed: REGULAR INTERVAL INSPECTION AND MAINTENANCE: at regular intervals not exceeding 1500 miles
Check all nuts, bolts, screws; wheel mounting socket screws; axle and rocker plate nuts

Wheels and tires

Factory

Factory: p11 items 10-12; first 1500 mi includes engine mounting bolts
Check spoke tension and wheel true

Wheels and tires

Factory

Manual: Check wheels for loose or broken spokes and rim damage. Factory: p11 item 13
Repack / replace wheel bearings

Wheels and tires

Factory

Manual: Lubricate wheel hubs (grease fittings). Factory: p11 item 3, p8-9 chart; 1000 mi in wet/dusty service
Check / repack sidecar wheel bearing

Sidecar

Factory

Manual: Lubricate sidecar wheel hub. Factory: p8: sidecar hub 1500 mi; other sidecar bearings 750 mi

Every 3,000 km or 12 months

3 items

Check rocker box oiling and pushrod tube seals for leaks

Engine

Guideline
Change gearbox oil

Primary and gearbox

Guideline
Check springer rocker stud play and spring condition

Front end

Guideline

Every 3,000 km

1 item

Change engine oil

Engine

Factory

Manual: Drain engine oil tank and refill with fresh oil. Factory: p8 item 19 and p10: at least every 2000 mi; first change at 750 mi; oftener dusty/winter

Every 5,000 km or 12 months

11 items

Check engine mounting bolts and plates

Engine

Guideline
Check throttle cable(s) free play and return

Fuel and air

Guideline
Check generator drive belt or chain

Ignition and electrics

Guideline
Adjust clutch pushrod / clutch adjuster

Primary and gearbox

Guideline
Check chain guard, chain oiler (if fitted), rear chain case

Final drive

Guideline
Inspect chain and sprockets for wear (measure stretch)

Final drive

Guideline
Check steering damper (friction or hydraulic)

Front end

Guideline
Check steering head bearing adjustment

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 wheel bearings for play

Wheels and tires

Guideline

Every 6,500 km or 12 months

2 items

Replace spark plugs

Engine

Guideline
Lubricate brake cam spindles, check linings and drums

Brakes

Guideline

Every 8,000 km or 12 months

1 item

Oil / check generator bearings (where an oiler is fitted)

Ignition and electrics

Factory

Manual: Pack generator commutator end bearing with grade A grease. Factory: p8 item 15 and p11: every 5000 mi or at least once a year

Every 8,000 km or 2 years

2 items

Check cylinder head bolt torque

Engine

Guideline

Air-cooled iron and alloy engines can lose head bolt tension; follow your manual's sequence and whether it is done hot or cold.
Flush oil tank and clean tank screen

Engine

Guideline

Every 9,500 km or 12 months

2 items

Check charging voltage and regulator / cut-out

Ignition and electrics

Guideline
Inspect generator brushes and commutator

Ignition and electrics

Guideline

Every 9,500 km or 2 years

2 items

Check engine breather and oil return

Engine

Guideline
Lubricate and check automatic advance unit

Ignition and electrics

Guideline

Every 13,000 km or 3 years

1 item

Decarbonize head, grind / lap valves (top-end decoke)

Engine

Guideline

Period practice. Leaded-era valve seats may need hardened seats for unleaded fuel.

Every 16,000 km or 2 years

1 item

Compression test (or leak-down)

Engine

Guideline

Every 16,000 km

1 item

Replace chain and sprockets (wear based)

Final drive

Guideline

Every 19,500 km or 3 years

1 item

Replace points and condenser

Ignition and electrics

Guideline

Every 24,000 km or 5 years

1 item

Inspect clutch plates and springs

Primary and gearbox

Guideline

Every 24,000 km

2 items

Replace brake linings / skim drums (wear based)

Brakes

Guideline
Lubricate speedometer / tachometer cables, check drive

Controls and cables

Factory

Manual: Lubricate speedometer core. Factory: p8: every 15,000 mi, core removed and fed through lubricant

Every 80,500 km

1 item

Repack / replace steering head bearings

Front end

Factory

Manual: Pack steering head bearings with grade A grease. Factory: p8 item 20: every 50,000 mi or when fork removed

Every 6 months

2 items

Clean battery terminals, check charge and strap

Ignition and electrics

Guideline
Lubricate manual advance / retard control and cable

Ignition and electrics

Factory

Manual: Remove, clean and grease spark and throttle control grips. Factory: p8 items 17/21: twice a year or when grips need it

Every 12 months

1 item

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

2 items

Inspect fuel tank for rust, sealer failure, leaks

Fuel and air

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

32 items

Initial Servicing of New Motorcycle, At First 1500 Miles: 1. Check condition of oil in tank to determine if oil change is needed.

Engine

Factory

Factory: As printed: At First 1500 Miles (one time)
Initial Servicing of New Motorcycle, At First 750 Miles: 1. Drain oil tank and refill with fresh oil.

Engine

Factory

Factory: As printed: At First 750 Miles (one time)
Initial Servicing of New Motorcycle, At First 750 Miles: 11. Inspect all wiring connections and tighten any found loose. Check switches, lights, etc.

Engine

Factory

Factory: As printed: At First 750 Miles (one time)
Initial Servicing of New Motorcycle, At First 1500 Miles: 14. Road test motorcycle to check carburetor adjustment and all-around performance.

Fuel and air

Factory

Factory: As printed: At First 1500 Miles (one time)
Initial Servicing of New Motorcycle, At First 750 Miles: 12. Check carburetor-manifold cap screws and manifold nuts.

Fuel and air

Factory

Factory: As printed: At First 750 Miles (one time)
Initial Servicing of New Motorcycle, At First 750 Miles: 13. Road test motorcycle to check carburetor adjustment and all-around performance.

Fuel and air

Factory

Factory: As printed: At First 750 Miles (one time)
Initial Servicing of New Motorcycle, At First 750 Miles: 5. If motorcycle is equipped with air cleaner, inspect and service if needed.

Fuel and air

Factory

Factory: As printed: At First 750 Miles (one time)
Initial Servicing of New Motorcycle, At First 1500 Miles: 12. Check level of battery solution and add distilled water if needed.

Ignition and electrics

Factory

Factory: As printed: At First 1500 Miles (one time)
Initial Servicing of New Motorcycle, At First 1500 Miles: 3. Lubricate all points indicated for 750 mile attention on Lubrication Chart.

Ignition and electrics

Factory

Factory: As printed: At First 1500 Miles (one time)
Initial Servicing of New Motorcycle, At First 750 Miles: 10. Check level of battery solution and add distilled water if needed. See that terminals are clean and connections tight.

Ignition and electrics

Factory

Factory: As printed: At First 750 Miles (one time)
Initial Servicing of New Motorcycle, At First 750 Miles: 3. Lubricate all points indicated for 750 mile attention on Lubrication Chart.

Ignition and electrics

Factory

Factory: As printed: At First 750 Miles (one time)
Initial Servicing of New Motorcycle, At First 1500 Miles: 2. Check level of oil in transmission and add oil if needed.

Primary and gearbox

Factory

Factory: As printed: At First 1500 Miles (one time)
Initial Servicing of New Motorcycle, At First 1500 Miles: 8. Check adjustment of clutch and clutch control. Adjust if needed.

Primary and gearbox

Factory

Factory: As printed: At First 1500 Miles (one time)
Initial Servicing of New Motorcycle, At First 750 Miles: 2. Check level of oil in transmission and add oil if needed.

Primary and gearbox

Factory

Factory: As printed: At First 750 Miles (one time)
Care and Lubrication of Drive Chains: Inspect the adjustment of chains at least every week and adjust them if necessary.

Final drive

Factory

Factory: As printed: at least every week (weekly interval, no month value)
Initial Servicing of New Motorcycle, At First 1500 Miles: 6. Check adjustment of chains. Adjust if needed. Again, check lubrication of front chain. Clean and lubricate rear chain and check for broken rollers, loose pins or cracked side plates.

Final drive

Factory

Factory: As printed: At First 1500 Miles (one time)
Initial Servicing of New Motorcycle, At First 250 Miles: 1. Check front chain to make sure it is receiving required amount of oil for ample lubrication. If necessary, readjust chain oiler.

Final drive

Factory

Factory: As printed: At First 250 Miles (one time)
Initial Servicing of New Motorcycle, At First 250 Miles: 2. Check adjustment of chains. Readjust if needed.

Final drive

Factory

Factory: As printed: At First 250 Miles (one time)
Initial Servicing of New Motorcycle, At First 750 Miles: 6. Check adjustment of chains and readjust if needed. Again, check lubrication of front chain and readjust chain oiler if found necessary. Clean and lubricate rear chain.

Final drive

Factory

Factory: As printed: At First 750 Miles (one time)
Initial Servicing of New Motorcycle, At First 750 Miles: 9. Check axle nuts and fork rocker plate stud nuts for looseness.

Front end

Factory

Factory: As printed: At First 750 Miles (one time)
General Lubrication, SIDECAR: Oil sidecar brake linkage regularly with oil can.

Brakes

Factory

Factory: As printed: regularly
Initial Servicing of New Motorcycle, At First 1500 Miles: 13. Engine should be given a complete tune-up including: Checking circuit braker points, ignition timing, valve tappets, spark plugs, draining and flushing carburetor bowl, cleaning and flushing gasoline strainer, carburetor adjustment, and cleaning muffler outlet. Service air cleaner if motorcycle is so equipped.

Brakes

Factory

Factory: As printed: At First 1500 Miles (one time)
Initial Servicing of New Motorcycle, At First 1500 Miles: 5. Oil all control joints, namely clutch, gear shifter, brakes, front brake control wire, and spark and throttle control wires at ends of their respective housings.

Brakes

Factory

Factory: As printed: At First 1500 Miles (one time)
Initial Servicing of New Motorcycle, At First 1500 Miles: 9. Check adjustments of brakes and brake controls. Adjust if needed.

Brakes

Factory

Factory: As printed: At First 1500 Miles (one time)
Initial Servicing of New Motorcycle, At First 750 Miles: 4. Oil all control joints, namely, clutch, gear shifter, brakes, front brake control wire, and spark and throttle control wires at ends of their respective housings.

Brakes

Factory

Factory: As printed: At First 750 Miles (one time)
Initial Servicing of New Motorcycle, At First 750 Miles: 7. Check adjustment of brakes. Readjust controls if needed.

Brakes

Factory

Factory: As printed: At First 750 Miles (one time)
Initial Servicing of New Motorcycle, At First 1500 Miles: 10. Check all nuts, bolts and screws and tighten any found loose. Particular attention should be given to engine mounting bolts, cylinder head bracket bolts or nuts, transmission mounting stud nuts, and wheel mounting socket screws.

Wheels and tires

Factory

Factory: As printed: At First 1500 Miles (one time)
Initial Servicing of New Motorcycle, At First 1500 Miles: 11. Check front and rear wheel for loose or broken spokes and rim damage.

Wheels and tires

Factory

Factory: As printed: At First 1500 Miles (one time)
Initial Servicing of New Motorcycle, At First 1500 Miles: 4. Lubricate wheel hubs at 1500 mile intervals as indicated on Lubrication Chart.

Wheels and tires

Factory

Factory: As printed: At First 1500 Miles (one time)
Initial Servicing of New Motorcycle, At First 750 Miles: 8. Check wheel mounting socket screws and tighten if needed.

Wheels and tires

Factory

Factory: As printed: At First 750 Miles (one time)
General Lubrication, CONTROLS: all control joints which are not provided with grease fitting should be oiled regularly with oil can, particularly after washing motorcycle or operating in wet weather.

Controls and cables

Factory

Factory: As printed: regularly, particularly after washing motorcycle or operating in wet weather
Initial Servicing of New Motorcycle, At First 1500 Miles: 7. Check adjustment of gear shifting control. Adjust if needed.

Controls and cables

Factory

Factory: As printed: At First 1500 Miles (one time)

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.