Classics & other

Yamaha SR 500

1978

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Vitals

Wet weight: 163 kg
Seat height: 810 mm
Fuel capacity: 12 L
Real world range: 220 km
Front tyre: 3.50-S19-4PR (lug type)
Rear tyre: 4.00-S18-4PR (lug type)
Tyre pressures: 1.8 / 2.0 kg/cm2 solo
Ground clearance: 165 mm

TerrainTarmac

Field repair

Fuse box: Under the seat, near the battery/CDI unit
Fuses: 1
Battery access: Under the seat

Kickstart starting procedure (cold and hot)

01Turn the fuel tap to 'on' and, for a cold start, pull the choke lever.
02Use the compression release lever to allow the kickstart to be positioned at the very top of its stroke without fighting engine compression.
03Release the compression lever once the kickstart is at the top of its stroke.
04Deliver one firm, full, committed kick through the entire stroke.
05For a hot restart, instead press the carburetor's hot-start button (located at the bottom of the carburetor body) to crack the throttle open slightly, then kick.
06If the bike is parked on a slope and kickstarting is unsuccessful after several attempts, push-start by getting the bike rolling and engaging the clutch in gear as an alternative starting method.
07As the engine warms, progressively ease off the choke.

Valve clearance adjustment (cold engine)

01Allow the engine to cool completely before checking clearances.
02Remove the valve inspection caps and rotate the engine to position the piston at top dead center on the compression stroke (both valves closed).
03Insert a feeler gauge between the rocker/adjuster and the valve stem: intake clearance 0.10mm, exhaust clearance 0.15mm.
04If out of spec, loosen the adjuster locknut, turn the adjuster screw to achieve the correct clearance, and re-torque the locknut while holding the adjuster stationary.
05Recheck clearance after tightening, then replace the inspection caps.

Drive chain adjustment and lubrication

01Place the motorcycle on its center stand with the rear wheel elevated.
02Check chain slack at the midpoint of the lower chain run against the factory spec of 20mm (0.8in).
03Loosen the rear axle nut and both chain adjuster nuts on the swingarm.
04Turn each adjuster evenly on both sides, using the swingarm alignment marks to maintain correct wheel tracking, until correct slack is achieved.
05Re-tighten the rear axle nut to factory torque, then the adjuster lock nuts.
06Lubricate the chain with SAE 10W/30 motor oil per factory manual guidance, applied while the chain is warm from riding for best penetration.

Carburetor float height check and idle mixture adjustment

01Turn off the fuel tap and remove the fuel line from the carburetor.
02Remove the float bowl from the base of the Mikuni VM34SS carburetor.
03Check float height against factory spec of 23.5mm plus or minus 1mm, adjusting the float tang if out of spec.
04Reinstall the float bowl with a fresh gasket if needed, then reconnect the fuel line.
05With the engine warm, adjust the idle speed screw to the factory target of 1,100 rpm.
06Fine-tune the pilot/mixture screw for the smoothest idle, noting the factory baseline is a preset (non-adjustable in some production runs) configuration on this model.

Data sheet

Dimensions & weights

Wet weight: 163 kg
Seat height: 810 mm
Ground clearance: 165 mm
Wheelbase: 1410 mm

Engine & drivetrain

Engine: 499 cc · Single
Cooling: Air cooled
Output: 32 hp · 37 Nm
Transmission: 5-speed
Final drive: Chain
Fuelling: Electronic fuel injection

Fuel & range

Fuel capacity: 12 L
Real world range: 220 km

Electronics & rider aids

Ride modes: None
Cruise control: No
Traction control: No
ABS: Yes
Heated grips: No
Heated seat: No

Service intervals

Service interval: 5,000 km
Chain lube: every 500 km

Protection

Bash plate: None
Radiator guard: No
Oil cooler guard: No
Hand guards: No

Consumables & service specs

Every value carries its source.

Tyres

Front: 3.50-S19-4PR (lug type)Yamaha SR500 1978-79 Factory Specifications
Rear: 4.00-S18-4PR (lug type)Yamaha SR500 1978-79 Factory Specifications

Tyre pressures

Front — solo: 1.8 kg/cm226 psi; solo rider, cold tyreYamaha SR500 Factory Service Manual
Rear — solo: 2.0 kg/cm228 psi; solo rider, cold tyreYamaha SR500 Factory Service Manual
Front — loaded: 2.0 kg/cm228 psi; at maximum load (315-365kg total) or high-speed ridingYamaha SR500 Factory Service Manual
Rear — loaded: 2.3 kg/cm232 psi; at maximum load (315-365kg total) or high-speed ridingYamaha SR500 Factory Service Manual

Engine oil

Viscosity: Yamalube 20W/40 motor oil or equivalentYamaha SR500 Factory Service Manual
Capacity: 2.4 lTotal amount 2.4L; periodic oil-only change 2.0L; full change with filter 2.1LYamaha SR500 Factory Service Manual

Brakes

Fluid type: DOT 3Hydraulic disc brakes front and rearYamaha SR500 1978-79 Factory Specifications

Forks

Oil capacity: 182 mlPer front fork leg (6.41 Imp. oz)Yamaha SR500 Factory Service Manual

Final drive

Chain: DID 50 HDSS, 103 links + joint, 15.875mm pitch (5/8in), 20mm free playNon-O-ring vintage chain typeYamaha SR500 1978-79 Factory Specifications

Spark plugs

Type: NGK BP7ES or Champion N-7YYamaha SR500 Factory Service Manual
Gap: 0.7-0.8 mm0.028-0.031inYamaha SR500 Factory Service Manual
Quantity: 1Single-cylinder engineYamaha SR500 1978-79 Factory Specifications

Battery

Type: 12N7-3B (G.S.), 12V 7AHYamaha SR500 1978-79 Factory Specifications

Fuel

Minimum octane: Regular gasoline (period spec, unleaded-compatible per factory manual); modern equivalent 87 AKI regular unleadedFactory specification sheet explicitly lists 'Regular gasoline' as the fuel grade, notable as this is a lower-compression (9.0:1) single that does not require premium fuel, unlike several of the other vintage vehicles in this setYamaha SR500 1978-79 Factory Specifications

What breaks first and where.

01

Hard/inconsistent kickstart-only starting (no electric start)

ModerateWidespread

The 1978 US-market SR500 was kickstart-only, and the model is widely known among owners for being temperamental to start, particularly when cold or, conversely, when hot. Correct technique — positioning the kickstart at the very top of its stroke using the compression release before delivering a full, committed kick — is essential; incorrect technique is a common cause of perceived 'hard starting' rather than a mechanical fault. A lean idle-jet condition (common on carburetors of this era) is frequently cited as compounding cold-starting difficulty; spark plug color (white/lean vs. brown-black/rich) is used as a diagnostic aid.

Symptoms

Difficulty starting when cold, requiring multiple precise kicks
Engine floods or fails to catch if kickstart technique is incorrect
Hot starting sometimes easier, sometimes harder, depending on individual bike/carb tuning
White (lean) spark plug insulator color on inspection

Field repairableYes — Use compression release to position kickstart at top of stroke before each kick; for hot starts, use the carburetor's hot-start button (cracks the throttle slightly); consider richening the idle/pilot jet if persistent lean-running symptoms are present; bump-starting on a slope is a practical workaround if kickstarting fails repeatedly.

Motorcycle Classics — Hard-Starting SR500