Triumph Bonneville T120

1959-1973.  650cc OHV air-cooled twin

T120R, T120RV, T120V, T120C, T120TT, T120RT

 

 

T120 Triumph Bonneville Pros

 

Performance: 110-115mph.

Looks: Most view the '59 T120 as the ultimate Triumph.

Reliable: Good, but expect niggling electrical issues.

Sound: Wonderful exhaust burble (but clattery top-end).

Spares: Most parts available without much trouble.

Re-sale: Bonnies sell easy. '59/'60 and '68/'69 in demand.

Investment: Excellent. Pre-units are still moving ahead.

Economy: 55-60mpg touring across the Bonneville range.

Maintenance: Straightforward. All problems understood.

Tuneable: Very. 750cc kits and hotter cams available.

Starting: Easy. Just tickle, prime, press, go and smile.

Gearbox: Early 4-speeds good. Later 5-speeds better.

Clutch: A little heavy, but reliable and competent.

Pre-unit construction: Traditionalists love this set-up.

Unit construction T120s: 1963-1970. The best all round?

Build: Special old-world quality to pre-unit Bonnevilles.

Coolness: Need a crowd?  Ride an early pre-unit example.

 

 

T120 Triumph Bonneville Cons

 

Handling: High speed wobbles. Feeble early frames.

Brakes: SLS drums inadequate. TLS Good. Marginal conicals.

Electrics: Bonnies are prone to vibration damage.

Lighting: Inadequate for high speed back roads.

Vibration: Crank balancing essential. Loose nuts are common.

Oil-in-frame: 1971-1973 models are less desirable.

Early-oil-in-frame: Seat is too high for many riders.

Suspension: Crude fork. Marginal rear springs/swinging arm.

Security: Pre-unit Bonnies are prime targets for thieves.

Top end: Often high wear rate (20k miles), but easy rebuild.

Riding position: Never ideal. Consider rear-sets, or similar.

Mechanical noise: Triumphs are famous for it. No big deal.

Prices: Pre-units are priced for collectors, not daily riders.

Carburettors: Twin set-up needs regular balancing/optimising.

Crank: Tip: strip old engines. Flush the sludge trap. Vital.

Zener diode: Pre-1966 T120s are 6-volt. Upgrade to 12-volt.

Oil leaks: Can be made oil tight, but few are. Still great bikes.

 

 

 


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