Triumph T120rv Bonneville

TRIUMPH T120RV BONNEVILLE

Cycle World Road Test

A Five-Speed Transmission Makes The Difference

THE LATEST BONNIE looks the same. But in Triumph terms, the addition of a five-speed gearbox to the venerable Bonneville is worth writing about.

The Triumph Twin hasn’t changed much from what it was 30 years ago. Increase displacement from 500 to 650cc. Incorporate in-unit gearbox design. Swinging arm rear suspension. Oil-in-frame chassis. Those are the big changes over three decades. And all the while, the gearbox has retained four speeds.

Triumph’s conservatism, a little island of calm in this age of annual obsolescence, makes it possible for one Triumph owner to recognize the other, even though their machines be dated several years apart. For the owner who keeps his machine awhile, it also makes sense at the parts counter.

But the modern world is not made up of people who keep their bikes indefinitely. As with everything else, bike owners are becoming more transient in regard to brand loyalty. Like the man says in “Future Shock,” the model citizen of tomorrow’s world does not tie himself to things or names. He does not cherish things. Instead, he uses them—until they are no longer useful.

So the world spins, and even the conservative, solid, gusty Triumph is caught up in the vortices of change, be it needed or not.

No, you don’t need a five-speed gearbox to enjoy the Triumph Bonneville. But it sure is neat. Hence, the optional Triumph T120 RV Bonneville.

What makes the RV box good is the fact that it brings the ratios closer together and eliminates some of the inertial problems in the old four-speed gearbox, which occasionally resisted speedy shifts from 1st to 2nd gear at high rpm.

It is almost impossible to tell that you have shifted, up or down, with the new five-speed. Lever travel is short. There is no crunch. There is no buzzsaw vibration on your right toe.

In operation, the new five-speed gearbox is similar to the four-speed unit. However, there are three shifter forks instead of the two employed on the four-speed. These forks now ride in recesses machined into the gears themselves rather than form a “girdle” which covers lips on the gears.

The layshaft is still supported by needle bearings, and the timing (right-hand) side of the mainshaft retains the ball bearing. However, a heavy-duty roller bearing with a large amount of bearing surface supports the drive side end.

This production five-speed unit is an improvement over some of the non-factory five-speed conversion kits which have been offered for several years in England in that it permits use of the kickstarter (don’t laugh), and has progressively narrower gear faces from 1st to 5th. The latter can be done because of the lesser amount of torque transmitted through the gearbox in the higher gears. The result is a savings in weight.

Our sole objection to the new set-up is the choice of overall drive ratio, a matter determined mainly by choice of rear and countershaft sprocket sizes. Both the four-speed and the five-speed have the same 4.95:1 top gear. This is Americanmarket oriented undergearing, which causes the engine to be turning over faster than necessary at freeway speeds. At 65 mph, the rpms are just under 5000.

This fast engine speed may be fine for a two-stroke Twin or big multi, but it reads out as unnecessary vibration on an English Twin. It’s not that Triumphs are bad for their kind, or getting worse, but that the other companies (including Norton) are doing something about the problem, either through engine isolation or redesign.

In the interim, the Triumph RV five-speed could be regeared higher to provide slower engine speed on the freeway, and thus reduce vibration. It will still have a low gear little higher than the four-speeder’s low gear. Now, the RV5s low is 12.82:1, the four-speeder’s is 12.08:1. Certainly the bike is capable of pulling a higher gear. And if you are a freeway man, your Triumph will last longer at the slower engine speed.

On a dragstrip, you can’t argue much with the gearing it’s got. The bike’s e.t. and trap time improved 0.3 sec. and 2 mph with no changes in engine output from the 1971 model. The extra speed and quickness at quarter-mile’s end is a direct benefit of the lower first gear, closer intermediate ratios, and smoother shifting between 1st and 2nd gears.

Dimensions of the RV are more suitable for shorter riders than before, but it appears that Triumph has ergonomically backed itself into a corner because of the dimensions of its recently introduced oil carrying frame. Our original complaint when we first rode the new generation Bonnie a year ago was that the seat, at 34.5-in., was too high. Triumph apparently thought so, too, for the seat has been lowered by the removal of padding, and dropping the front end of the bike with shortened fork springs. Unfortunately the chop job leaves you with a hard seat that slopes slightly backward.

By the time you read this, some 197214 changes will have been incorporated by Triumph. The present gasoline tank, which holds 3.5 gal., will be replaced by a 2.5-gal. slimline model. It won’t give you much range, but it will be “cosmetic.” Further, the ’7234 model will incorporate bolt-on single rockerbox covers, one for the two intake valves and one for the two exhaust valves. This replaces the separate screw-in caps that seem to vibrate loose with some frequency.

The Bonneville either as a four-speeder or optional fivespeeder is unequivocally one of the best handling roadsters in its size category. For one thing, it doesn’t feel like it weighs 410 lb. wet. It points easy, and tracks well. Steering is light and fast. On some very bumpy surfaces, we felt the machine would benefit from an adjustable steering damper; even so, at no time did any front wheel perturbations seem like they’d get out of hand.

The braking figure obtained from 60 mph—an impressive 118 feet—tells you all you need to know about Triumph’s recently introduced conical hub brakes. They work beautifully, with excellent progression and feedback, and don’t fade.

In the English tradition, or what seems to have become one, the bike weeped some oil, leaving a light film and some droplets on the pipes, cases and back wheel. In cleanliness, then, the Bonneville is about par for a Limey bike. And certainly it is staying drier than it would have a few years ago.

The only thing that makes us gasp a little is the price. Seventeen hundred bucks is the price of a new small car, if you shop wisely. It is also the price of some heavy-duty competition from Japan. Yes, the five-speed gearbox is nice, but is it $200 nicer than the four-speed?

Perhaps, to a Triumph lover, price is no object. Maybe Triumph lovers are like Porsche lovers, who insist on paying $10,000 for a car that looks like $5000 and love every minute of it.

TRIUMPH

T120 RV BONNEVILLE

List price .........................$1725