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.

Triumph ought to have given the T120 variants different designations. Why? Because there are three essential types; the original 1959 pre-unit Bonnies (image left, which are highly desirable and fetch big money; the unit-construction bikes from 1963-1970 (generally viewed as the best compromise between looks, handling, outlay and investment); and the later (and cheaper) oil-in-frame models (much derided for their more staid looks, conical hub brakes, and high saddles). But these latter Bonnies are rising in value as they become more "classic".

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The Bonneville was so named to cash in on Johnny Allen's record breaking speed run at the Utah salt flats in 1956 (214.17mph) even though the Meriden firm did not support the attempt. Interestingly, the 1959 Bonnie was built and marketed as a tourer, but people think of them as sporting machines.

In terms of value for money, the oil-in-frame (OIF) Triumph Bonnevilles are best. Yes, build quality was variable with these final bikes. But everything can be retro-engineered making OIF's excellent all-around machines that aren't too expensive or too precious to worry about.

Bonnies are perhaps the best all-round British classic bikes. Fast enough, smooth enough, and agile enough. And, of course, they just look so good. Try one.