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Triumph Tiger 750

1973
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Triumph Tiger 750 — 1973
Image: The Marquis (1973 Triumph Sales Brochure) — Triumph Engineering Company Limited

Vitals

Wet weight
179.3 kg
Seat height
826 mm
Fuel capacity
13.6 L
Real world range
280 km
Front tyre
3.25 x 19
Rear tyre
4.00 x 18
Tyre pressures
24 / 24-25 psi solo
Ground clearance
127 mm
TerrainTarmac

Field repair

Fuse box
Under the seat, inline with the main wiring harness near the battery
Fuses
1
Battery access
Under the seat, in a side-mounted battery carrier within the oil-in-frame backbone structure

Points ignition timing and gap adjustment

  1. 01Remove the contact breaker cover on the right-hand side of the engine.
  2. 02Rotate the engine until the points cam lobe presents the point set at full separation.
  3. 03Loosen the points-plate screw slightly and insert a 0.35-0.40mm (0.014-0.016in) feeler gauge between the contact faces.
  4. 04Adjust the fixed contact position until the feeler gauge is a light drag fit, then retighten the screw.
  5. 05With points gap set, rotate the engine to the full-advance timing mark (38° BTDC) and use a test light or timing strobe to verify the points open exactly at this mark; rotate the baseplate as needed and retighten.
  6. 06Repeat the gap check for the second cylinder's point set, since the two are typically independently adjustable on twin-cylinder point sets of this era.

Kickstart procedure and cold-start technique

  1. 01Turn on the fuel taps and pull the choke/air lever for a cold start.
  2. 02Tickle the Amal Concentric carburetor(s) briefly by pressing the float chamber tickler pin until fuel just shows at the overflow, indicating the float bowls are full.
  3. 03Slowly rotate the kickstart lever with the ignition off (or in neutral) to find top dead center/compression resistance, then ease back just past this point to position for the kick.
  4. 04Turn on the ignition, then deliver one firm, full-stroke kick.
  5. 05Once running, progressively close the choke as the engine reaches operating temperature.

Amal Concentric carburetor float bowl access and float height check

  1. 01Turn off the fuel tap and remove the fuel line from the carburetor inlet.
  2. 02Remove the float bowl retaining screw(s) at the base of the carburetor body and lower the float bowl away.
  3. 03Inspect the float and float needle for wear, and check the float height/level against factory spec, adjusting the float tang if necessary.
  4. 04Clean the float bowl of any sediment and inspect the main jet (factory spec: main jet #280, needle jet .106) for debris.
  5. 05Reinstall the float bowl with a fresh gasket if the old one shows compression set or damage, then reconnect the fuel line and check for leaks before riding.

Drive chain adjustment on wingnut-style rear axle

  1. 01Place the motorcycle on its center stand with the rear wheel elevated.
  2. 02Check chain slack at the midpoint of the lower chain run.
  3. 03Loosen the rear axle nut and both chain adjuster wingnuts on each side of the swingarm/chainstay.
  4. 04Turn each wingnut adjuster evenly to move the wheel rearward (tightening chain) or forward (loosening chain), using the swingarm alignment marks to maintain correct wheel tracking.
  5. 05Verify equal adjustment on both sides before re-tightening the rear axle nut to factory torque.
  6. 06Recheck chain slack and wheel alignment after final tightening.

Data sheet

Dimensions & weights

Wet weight
179.3 kg
Seat height
826 mm
Ground clearance
127 mm
Wheelbase
1403 mm

Engine & drivetrain

Engine
744 cc · Parallel twin
Cooling
Air cooled
Output
52 hp · 54 Nm
Transmission
5-speed
Final drive
Chain
Fuelling
Electronic fuel injection

Fuel & range

Fuel capacity
13.6 L
Real world range
280 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
3.25 x 19Trojan Classics — 1973 Triumph Unit 750 Technical Data
Rear
4.00 x 18Trojan Classics — 1973 Triumph Unit 750 Technical Data

Tyre pressures

Front — solo
24 psiPer Hermit.cc Triumph 650/750 maintenance manual (1.68 kg/cm2); note the later 1978 T140E handbook gives a higher 28psi front figure — the earlier 24psi figure is used here as more contemporaneous to 1973, but a documented running change to higher pressures likely occurred later in production.Hermit.cc Triumph Unit Twin Maintenance Manual
Rear — solo
24-25 psiPer Hermit.cc Triumph 650/750 maintenance manual, varies slightly by variant; the later 1978 T140E handbook gives 32psi rear — flagged as a likely later running change, not confirmed 1973-specific.Hermit.cc Triumph Unit Twin Maintenance Manual

Engine oil

Viscosity
SAE 20W-50 (multi-grade, later spec); non-detergent straight-40 was period-correct at introductionHermit.cc manual notes multigrade 20W-50 for later unit-construction 650/750 models; earliest 1973 production likely still specified non-detergent single-grade oil per period British practice, with a 3,000-mile change interval on non-detergent oilHermit.cc Triumph Unit Twin Maintenance Manual
Capacity
3.4 l7.25 Imperial pints, later-model oil-in-frame tank capacity per Hermit.cc manual; the 1973 factory technical data sheet separately states oil tank capacity as 4.8 US pints (approx. 2.3L) — a discrepancy likely reflecting different measurement conventions or a running change; both figures are presented for transparency, with the Trojan Classics 1973-specific sheet given priority as the primary year-specific sourceTrojan Classics — 1973 Triumph Unit 750 Technical Data

Brakes

Fluid type
DOT 3Front disc brake hydraulic system (10in Lockheed 2-piston caliper introduced on 1973 TR7RV); per later 1978 T140E handbook, likely consistent for 1973 given the shared Lockheed disc system1978 T140E Owner's Handbook (classicbike.biz)

Forks

Oil capacity
190 mlPer front fork leg, per 1973 factory technical data sheetTrojan Classics — 1973 Triumph Unit 750 Technical Data

Final drive

Chain
Primary: Triplex, 84 links; Secondary (rear drive): 5/8 x 3/8in, 107 linksNew-for-1973 triplex primary chain (upgraded from earlier duplex); enclosed oil-bath primary chaincase, open non-O-ring rear chainTrojan Classics — 1973 Triumph Unit 750 Technical Data

Spark plugs

Type
Champion N3Also cross-referenced as Champion N-3 in Hermit.cc manualTrojan Classics — 1973 Triumph Unit 750 Technical Data
Gap
0.635 mm0.025inHermit.cc Triumph Unit Twin Maintenance Manual
Quantity
2Parallel-twin engine, one plug per cylinderTrojan Classics — 1973 Triumph Unit 750 Technical Data

Fuel

Minimum octane
97 RON (period premium leaded); modern equivalent 91-93 AKI premium unleaded plus lead-substitute additive recommended for non-hardened valve seatsPer 1978 T140E owner's handbook minimum octane spec, carried forward as a reasonable reference for the closely related 1973 unit-construction 750 engine1978 T140E Owner's Handbook (classicbike.biz)

What breaks first and where.

01

Oil-in-frame reservoir leak points

ModerateCommon

The 1971-onward 'oil-in-frame' (OIF) Triumph twins use the steel frame's front downtube/backbone structure as the engine oil reservoir. The 1973-on frames used a different reservoir oil feed and gauze strainer configuration than the initial 1971-72 OIF design. Common leak points occur at the frame-to-oil-tank joints, the filler cap seal, and the return-pipe connection at the base of the frame; a further production change during 1977 extended the rigid oil return pipe to a position below the airbox. On the smaller-displacement 650 OIF frames, cracking around the swinging arm pivot was also a source of leaks, though the 750 frames (as used on this 1973 Tiger) are described by enthusiasts as notably improved in this respect.

Symptoms

  • Oil seepage at frame downtube joints or filler cap
  • Oil staining around the frame backbone near the steering head or swingarm pivot
  • Gradual loss of oil level in the frame reservoir

Field repairableYes — Reseal frame joints and filler cap with fresh gaskets/sealant; inspect and clean the gauze strainer at the tank outlet; on 650 frames specifically, inspect the swingarm pivot area for cracking, which requires more extensive frame repair or replacement if found.

Classic Motorcycle Forum — OIF Frames
02

High oil pressure / oil-in-frame tank pressure relief issues

MinorOccasional

Owner reports on the oil-in-frame Tiger/Bonneville twins describe instances of unexpectedly high oil pressure readings related to the frame oil tank's pressure release valve and feed configuration, particularly on 1973-model-year bikes. The pressure relief valve is located at the front of the engine; typical readings are approximately 80psi cold start, 65-80psi hot running, and 20-25psi hot idle — deviations from this range prompted forum troubleshooting discussions.

Symptoms

  • Oil pressure gauge reading persistently above the expected hot-running range
  • Uncertainty distinguishing a genuine relief-valve fault from a normal reading for the oil-in-frame design

Field repairableYes — Inspect and clean the pressure relief valve at the front of the engine; verify against the documented normal ranges (approx. 80psi cold start / 65-80psi hot running / 20-25psi hot idle) before assuming a fault.

The Triumph Forum — High Oil Pressure Thread