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

EL / FL Knucklehead

Library entry covers 1936-1947

27 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).

Open the source

72 items for a 1940 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

1940 Harley-Davidson EL / FL Knucklehead

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 500 mi

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 600 mi

1 item

Check chain slack and rear wheel alignment

Pre-ride / on the road

Guideline

On the road: every 1,000 mi

1 item

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

Pre-ride / on the road

Guideline

Every 750 mi

2 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
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 1,000 mi or 6 months

1 item

Inspect tire tread, sidewalls and date codes

Wheels and tires

Guideline

Every 1,000 mi or 12 months

1 item

Grease saddle pivot, check saddle springs / seat post

Rear suspension and frame

Guideline

Every 1,000 mi

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 1,500 mi

18 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
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
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
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
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 2,000 mi 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 2,000 mi

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 3,000 mi 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 4,000 mi or 12 months

2 items

Replace spark plugs

Engine

Guideline
Lubricate brake cam spindles, check linings and drums

Brakes

Guideline

Every 5,000 mi 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 5,000 mi 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 6,000 mi 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 6,000 mi or 2 years

2 items

Check engine breather and oil return

Engine

Guideline
Lubricate and check automatic advance unit

Ignition and electrics

Guideline

Every 8,000 mi 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 10,000 mi or 2 years

1 item

Compression test (or leak-down)

Engine

Guideline

Every 10,000 mi

1 item

Replace chain and sprockets (wear based)

Final drive

Guideline

Every 12,000 mi or 3 years

1 item

Replace points and condenser

Ignition and electrics

Guideline

Every 15,000 mi or 5 years

1 item

Inspect clutch plates and springs

Primary and gearbox

Guideline

Every 15,000 mi

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 50,000 mi

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

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.