Triumph Thunderbird big-bore

Since its release in the last quarter of 2009, the Triumph Thunderbird parallel twin has firmly established itself as a sporting cruiser par excellence, as well as filling a gaping hole in the British marque's line-up between the perennially popular 865cc America and Speedmaster, and the gargantuan 2.3-litre Rocket III Roadster.

It hooks up with serious purpose, and has personality written all over the powerplant, which shares the same 270-degree crank throw as the America and Speedmaster to provide the "kind of sound and feel that cruise customers expect".  The engine, which is totally new besides sharing the same valves as the Rocket III, produces 86hp at 4850rpm and 146Nm at an effortless 2750rpm.

And did we mention the smooth-shifting helical-designed gearbox and the excellent road manners? The only real shortcomings are the minimal ground clearance (even for a cruiser) and the rear suspension, which does have its limitations at higher speeds - but something that most people would be oblivious to when they are cantering along at 110km/h.

The rear tyre is a manageable 200-section, and for 330kg of cruiser it does steer well and there's plenty of agility, which belies its raked-out geometry and 1615mm wheelbase. Even U-turns are a breeze.

Click on the following link for the full launch report on the Thunderbird.

The Bikesales Network has now revisited the Thunderbird, but this time in big-bore guise which has lifted capacity from 1597cc to 1699cc. And if you think the standard engine is dripping in character, the big-bore leaves it ashen-faced with power increasing from 85 to 100hp (when fitted with aftermarket silencers) and torque from 146 to 165Nm. It really is a jewel.

Triumph has achieved the capacity increase by adding 3.3mm to the bore, which means the already massive pistons (already bigger than the Rocket's) are now 107.1mm wide.

The big-bore kit includes cams, pistons, rings, liners and gaskets, and a new downloadable tune to complete the conversion. It is homologated for most markets, but only when dealer fitted and in conjunction wit the standard silencers.

As well as the big-bore kit, which costs around $2500 fitted (there's about 10 hours' labour involved), the big-bore Thunderbird was also adorned with just about every conceivable accessory from the Triumph catalogue to complete the masterpiece. It adds another $7811 (plus labour) to the price.

The bling is as follows:

FLYSCREEN KIT  $319
SILENCER KIT SHORT $665
CHROME REAR PULLEY $739
CHROME SWINGARM COVER $245
BIG BORE PERFORMANCE KIT $1,195
CHROME LOWER BELT GUARD $169
CHROME WHEEL KIT $1485
CHROME FORK SLIDER KIT $739
CALIPER CAPS, CHROME $69
REAR CALIPER CAP, CHROME $35
REAR MASTER CYLINDER, CHROME $55
OIL FILLER CAP, BADGE $75
POLISHED OIL GALLERY $39
CHROME CLUTCH LIFTER $48
INSTRUMENT VISOR, CHROME $59
RR FENDER EMBELL MEDALION $26
CHROMELINE RIDER FOOT PEG $195
CHROMELINE GEAR SHIFT $55
SMALL BRAKE PEDAL FINISHER $61.80
SINGLE SEAT RACK, PRESSED $195
TWIN T HANDLEBAR $295
HOUSING SWITCH KIT $455
CLAMP, SWITCHCUBE, CHROME $39
CHROME LEVERS $175
OVAL MIRRORS, DRILLED $254
MASTER CYLINDER COVER $125
    
Some cruisers demand chrome to give them an aesthetic edge, but I don't reckon the Thunderbird falls into that category - especially as the parallel twin engine has such an authoritative look and is a departure from the standard cruiser V-twin fare. And there's no external plumbing (oil and water pipes, etc) to tarnish the picture.

Still, some of the chrome adornments are gorgeous, especially the smaller bits and pieces such as the master cylinder covers.

But back to the engine. I sort of knew what to expect, as a mate of mine (who incidentally shares the same first name and birthday as me) had purchased a Thunderbird with the kit only weeks earlier. I had been telling him that bigger was undoubtedly better, and he fell for my rhetoric. I then went for a brief ride, and the rhetoric was reality within seconds.

I then moved onto Triumph Australia's version, and the feeling of quality engagement was much the same. The big-bore is undoubtedly a bit more of a rough diamond than the standard jobbie, and by that I mean it snorts and pops just a little bit more, and there's a little more mechanical noise.

But what it lacks in refinement the big-bore makes up for in sheer brawn, and it's the 13 per cent increase in torque (give or take a smidgeon depending on rpm) which really lays out the welcome mat. Pushing the big-bore into overrun territory is bliss, as is lurching from one corner to another without having to worry about changing gears to maintain momentum. I barely revved the big-bore above 4000-5000rpm, because there's really no point unless you're looking to get a mega move on.

Maximum torque on the big-bore is now 3000rpm compared to 2750rpm on the standard, which is still ridiculously low and accommodating. And you will travel long distances on the Thunderbird, with the engine barely ticking over in top gear - great for fuel economy.

I don't believe the 1597cc version needs six gears, and that's definitely the case for the big-bore - it could even get away with four cogs. But six it is, and I could think of worse 'crimes' than playing with this sweet-shifting and clunk-less gearbox.

If you can afford the bigger financial hit for the big-bore, just do it. Bigger is certainly better.

SPECS: TRIUMPH THUNDERBIRD BIG-BORE

ENGINE
Type: Liquid-cooled, eight-valve, DOHC parallel twin, 270-degree firing order
Capacity: 1700cc
Bore x stroke: 107.1mm x 94.3mm
Compression ratio: 9.7:1
Fuel system: Electronic fuel injection
Emissions: Euro 3

TRANSMISSION
Type: Six-speed wit helical gears
Final drive: Belt

DIMENSIONS AND CAPACITIES
Claimed dry weight: 308kg
Claimed wet weight: 339kg
Seat height: 700mm
Wheelbase: 1615mm
Fuel capacity: 22lt

PERFORMANCE
Claimed maximum power: 100hp at 4850rpm
Claimed maximum torque: 165Nm at 3000rpm

OTHER STUFF
Price: $20,990 (ABS: $21,990)
Big-bore kit: $1195 plus labour (8-10 hours)
Colours: Jet Black, Pacific Blue/Fusion White, or Aluminium Silver/Jet Black
Bike supplied by: Triumph Australia (www.triumphmotorcycles.com.au)
Warranty: 24 months, unlimited kilometres