Bridge­stone’s disc-valve, 350 GTR two-stroke was a ma­chine way ahead of its time when it hit the streets in ’67

Classic Bike (UK) - - Bridgestone 350 Gtr - WORDS: GEZ KANE. PHO­TOG­RA­PHY: GARY FREE­MAN

Carv­ing my way through the rush­hour traf­fic on the out­skirts of Manch­ester, I’m be­com­ing in­creas­ingly im­pressed by the bike I’m rid­ing. Partly, that’s be­cause it feels more like a rider’s ma­chine than a show pony. Oh, it’s tidy all right, but it proudly wears the patina of its 50 glo­ri­ously un­re­stored years – and owner Alis­ter Vick­ers has got it set up per­fectly. But it’s also be­cause it’s a very fine mo­tor­cy­cle.

It starts with just a prod on the left-hand kick­start, the brakes work per­fectly, the clutch is light and pro­gres­sive and there’s plenty of zip in the 345cc en­gine. I’ve never had the plea­sure of rid­ing a Bridge­stone 350 GTR be­fore, but I’m rapidly com­ing to the con­clu­sion that that’s what it is – a real plea­sure.

Bridge­stone weren’t shy about singing the praises of their mid­dleweight twin when it hit the streets in 1967. ‘The most ad­vanced mo­tor­cy­cle ever built,’ trum­peted their Amer­i­can sales literature. The thing is, though, un­like many an ad­ver­tis­ing claim, this one might just have been true. Let’s look at the specs: six-speed gear­box, a claimed 40bhp, a top speed over the magic ton, twin-lead­ing­shoe front brake and au­to­matic lu­bri­ca­tion with pres­sure feed to the main bear­ings.

Fair play, Suzuki had all that a year ear­lier on their 250cc T20, but the GTR throws ro­tary valve in­duc­tion into the mix. And there’s a host of top qual­ity de­tail touches like the built-in ca­ble-oil­ing nip­ples, stain­less steel front mud­guard and a dou­ble-sided gearchange shaft that al­lowed diehards to mount the gearchange on the right – just like on the Bri­tish bikes that the Bridge­stone mar­ket­ing depart­ment hoped they’d aban­don in droves. OK, maybe the GTR wasn’t quite the most ad­vanced mo­tor­cy­cle

ever built – but it was cer­tainly very good.

The 350 GTR was cer­tainly Bridge­stone’s high wa­ter mark as a mo­tor­cy­cle man­u­fac­turer, though. The com­pany may be best known for its tyres, but it moved into bi­cy­cle pro­duc­tion in the af­ter­math of World War II and then into the clip-on en­gine mar­ket as many of its com­peti­tors – in­clud­ing Honda – also did.

From buy­ing in en­gines ini­tially, Bridge­stone steadily im­proved its two-wheeled of­fer­ing, pro­duc­ing its first mo­tor­cy­cle – the 50cc Cham­pion – in 1958. The Bridge­stone range grad­u­ally ex­panded, get­ting a ma­jor boost by the re­cruit­ment of ex-lilac and To­hatsu en­gi­neers fol­low­ing the demise of their re­spec­tive com­pa­nies. The 1964 BS90 – fol­lowed in 1965 by the BS50 and BS175, and in 1967 by the BS350 – was the re­sult.

The en­tire range used disc-valve en­gines, which would set the tem­plate for Bridge­stone motorcycles un­til pro­duc­tion ceased in 1971. That ces­sa­tion was not a re­flec­tion on the ex­cel­lent motorcycles the firm pro­duced, but rather a re­sult of the grow­ing de­mands of the thriv­ing tyre pro­duc­tion lines, pos­si­bly a lit­tle com­mer­cial pres­sure from other man­u­fac­tur­ers who bought vast quan­ti­ties of tyres for their own ma­chines, and also the fact that Bridge­stone qual­ity didn’t come cheap. In the UK – where Bill Smith Mo­tors were the sole im­porters – the 350 GTR cost al­most as much as a Tri­umph or BSA 650.

But, if motorcycles had to make way for tyre man­u­fac­ture, the bikes that Bridge­stone pro­duced be­fore call­ing it a day stand com­par­i­son with the best of their ri­vals. To show­case their engi­neer­ing prow­ess, Bridge­stone pro­duced an in­no­va­tive, wa­ter­cooled 50cc road racer rid­den at the Dutch TT by Tommy Robb, Jack Find­lay and Isao Mor­ishita in 1966; a 250cc mo­tocross ma­chine that won the Ja­panese na­tional cham­pi­onships in 1965; and the SR se­ries pro­duc­tion rac­ers, aimed at the US dirt track and mo­tocross cir­cuit. But, of the road bikes, the 350 GTR was the pin­na­cle of Bridge­stone’s achieve­ment.

The ro­tary disc-valve en­gine is a gem. Us­ing disc valves to con­trol port tim­ing meant the Bridge­stone en­gine de­vel­oped more torque at lower revs than its pis­ton-ported

con­tem­po­raries. The crank­shaft is a mas­sive, pressed-up four-bear­ing job with a labyrinth seal at the cen­tre. A pair of disc valves are mounted on the crank­shaft, one on each end, while the brace of Mikuni carburettors clamp to stubs on the valve cov­ers, en­closed in neat cast al­loy cov­ers.

To keep the en­gine ac­cept­ably nar­row, the al­ter­na­tor is mounted be­hind the bar­rels on top of the gear­box. And the in­no­va­tion didn’t stop there, ei­ther. In­stead of the more fa­mil­iar iron lin­ers, Bridge­stone pi­o­neered the use of plated chrome bar­rels – the first time the tech­nol­ogy had ever been ap­plied to a road bike. There’s even a dry clutch in there. It’s all clever stuff and the re­sult is that the GTR is one of the fastest and most re­li­able 350s of its era.

That’s one of the things that at­tracted cur­rent owner Alis­ter to the bike in the first place. “I re­mem­ber read­ing a road test in an old mag­a­zine from years back,” he re­calls. “The tester was amazed at how fast the bike was and I thought: ‘That’s the bike for me’. I love two-strokes any­way and I re­ally like orig­i­nal bikes, so this one ticked both those boxes. Mal­colm An­der­son from the Kawasaki Triples Club – yes, I’m into those, too – bought it at the Stafford show some years ago. It’s a US im­port, and as soon as I saw it I said I’d buy it. Mal­colm didn’t re­ally like it, so he said I could have it when­ever I could raise the cash.

“I fi­nally bought it four years ago. When I got it, it had RD250 in­di­ca­tors bodged on, with a switch clipped to the han­dle­bars. I soon got rid of those. The rest of the bike is to­tally orig­i­nal and the 3884 miles on the clock are gen­uine. It’s a re­ally early ex­am­ple – the frame num­ber is from the first week of pro­duc­tion. It doesn’t get any bet­ter than that for me.”

Alis­ter’s en­thu­si­asm for a bike that must have seemed way ahead of its time is ob­vi­ous, but I need to see for my­self what the fu­ture looked like in 1967. ‘Pretty good’ is the short an­swer. I get the chance to try out that tls brake al­most straight away, as a set of traf­fic lights changes to red on a steep hill. There’s bags of feel at the lever and it’s eas­ily as good as any early disc stop­per, de­spite be­ing the same unit as on the

much lighter Bridge­stone 175 twin, while the big sin­gle-lead­ing-shoe rear pro­vides plenty of ex­tra stop­ping power when I need it in a hurry.

There’s no doubt, though, that it’s the un­usual-look­ing en­gine that gives the GTR its soul. With the slightly boxy cases for the carburettors hung on the side of the crankcases it might not be the most classically beau­ti­ful power plant of 1967, but boy does it de­liver. There’s un­ex­pected torque at min­i­mal revs that makes pot­ter­ing round town a plea­sure. But crack open the throt­tle and the GTR leaps for­ward like a Lurcher af­ter a rab­bit.

Although there’s am­ple low-down urge, from around 4000rpm the GTR re­ally gets a move on. Peak power ar­rives at 7500rpm ac­cord­ing to Bridge­stone, but the red­line – or more ac­cu­rately red band, as it lasts for 2000rpm – on the tacho starts at a more con­ser­va­tive 6000rpm, and keep­ing the revs down to that level still pro­vides plenty of go. Pe­riod road tests threw up a va­ri­ety of top speeds for the GTR, but I’d cer­tainly be sur­prised if this one wouldn’t top the ton – punch­ing well above its weight for a 350 in 1967.

In a week of un­usual gear­boxes (I’ve also been rid­ing a Suzuki TC250 and a Kawasaki H2) the six-speed gear­box of the GTR throws an­other vari­able at me. From neu­tral, all the gears are down on the left-foot change. That means that chang­ing down right through the ’box can leave me back in neu­tral when I’m least ex­pect­ing it. But I soon get the hang of it – though there’s a slightly puz­zling yel­low warn­ing light on the speedome­ter that il­lu­mi­nates to let me know when I’m in fifth gear. Pre­sum­ably, Bridge­stone didn’t want their cus­tomers for­get­ting what a high-tech piece of kit they were rid­ing and that they still had an­other ra­tio to go.

If the en­gine’s power char­ac­ter­is­tics of­fer the best of both worlds, so too does the phys­i­cal size of the bike – for a rider of my stature any­way. All too of­ten, the plea­sure of a lively mid­dleweight can be dulled a touch by a cramped rid­ing po­si­tion and an un­com­fort­able feel­ing that I must look faintly ridicu­lous perched atop a bike that’s a size too small. There’s no chance of that with the GTR.

Per­haps to look more im­pos­ing for the ‘big­ger is bet­ter’ Amer­i­can mar­ket – where a mere 350 could be re­garded as a toy back in the ’60s – the Bridge­stone is re­as­sur­ingly roomy. The 19in wheels help, of course, but the stiff, twin-down­tube frame is fairly tall, too, while a

seat height top­ping 32in and those high ’bars means taller rid­ers can stretch out a bit. The rel­a­tively lofty rid­ing po­si­tion also gives the bike and its rider more pres­ence when ne­go­ti­at­ing town traf­fic and, once out on more open roads, there’s plenty of room to move around. Ideal for traf­fic-split­ting in town or hus­tling along B-road swervery.

Even the sus­pen­sion was the sub­ject of care­ful con­sid­er­a­tion by the Bridge­stone de­sign­ers. While the forks are con­ven­tional enough, with their ex­ter­nal springs dis­creetly con­cealed by prac­ti­cal rub­ber gaiters, the con­ser­va­tively chrome-shrouded rear shocks have been pro­vided with a choice of two top mount­ings to stiffen or soften the sus­pen­sion move­ment by vary­ing the an­gle of the shocks’ ac­tion. And, while the sus­pen­sion on Alis­ter’s bike may have soft­ened over the years, and I’m sub­jected to a bit of a jolt­ing on the pot­holed Cheshire lanes, the GTR never feels like it’s go­ing to step out of line.

De­spite the ob­vi­ous care and at­ten­tion lav­ished on prac­ti­cally all as­pects of the GTR’S de­sign, there are no un­nec­es­sary frip­peries. No elec­tric start and no in­di­ca­tors (ap­par­ently they were avail­able as an op­tional ex­tra). There’s not even any brand­ing to spoil the ex­panse of scal­loped chrome side-pan­els on the slim and stylish fuel tank. In­stead, the Bridge­stone name is em­bla­zoned boldly along each side of the seat above the rear wheel, while the seat it­self is topped with faux-suede pan­els that grip my jeans se­curely. Per­fect when prac­tic­ing the 13.7s stand­ing-start quar­ters Bridge­stone pub­lic­ity ma­te­rial boasted of. The Bridge­stone is all about de­liv­er­ing quart per­for­mance from a pint-pot pack­age. And it does. It must have been a rev­e­la­tion in 1967.

But while there may be no su­per­flu­ous gad­getry, that’s not to say the Bridge­stone is poorly spec­i­fied. Quite the op­po­site, in fact. A rev counter is stan­dard, there’s a fric­tion damper and oil in­jec­tion, too. There’s even a sight glass to see how much two-stroke oil is left in the tank. And the build qual­ity is ahead of any of its ri­vals from the day.

In fact, this is a bike that’s still a more than ca­pa­ble tool in today’s traf­fic con­di­tions. Fast enough, stops well, steers well – and looks good, too. It’s hard to be­lieve it’s 50 years old. Sadly, you don’t see too many Bridge­stone 350 GTRS on the road, but if you get the chance to beg a ride on one, grab it. I guar­an­tee you’ll be might­ily im­pressed. Back in 1967 the GTR must have seemed like a vi­sion of the fu­ture. You could cer­tainly give rid­ers on a 650 Brit twin a fright on the Yamaha LC’S spir­i­tual grandad. It re­ally is that good.

ABOVE: En­gine is sur­pris­ingly torquey low down, and re­ally gets a move on as the revs rise LEFT: Light­ing this up is a sat­is­fy­ing ex­pe­ri­ence. The brakes are good

Au­to­matic lu­bri­ca­tion with pres­sure feed to main bear­ings was one of the high­tech fea­tures

Disc valves and carbs live un­der these al­loy cov­ers

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