The Bridgestone 350GTR is an extremely rare motorcycle in the UK. It's probably a very rare motorcycle everywhere in the world, come to that. I have not seen any others on the road. I bought my 1967 model from an old gent who had owned it from new, put only 12,400 miles on the clock and had a couple of boxes full of spare engine parts - just as well as they are otherwise unavailable. He claimed to have something to do with the importers, hence the spares.
The owner seemed genuine, the price was low when compared to what you'd have to pay for a British classic of the same era and the brief test ride showed the bike as basically sound. A few engine noises could be put down to the bike's age rather than any impending mechanical doom. Well, you know how it is with motorcycles, after your first glance you usually know if you are going to buy or not and I liked the style of this most rare machine.
The bike was manufactured by the same people who make the tyres in good old Japan, they eventually selling off their motorcycle interests in favour of concentrating on the rubber business. A two stroke twin that developed 40 horses, which for 1967 was very good going. The usual problems with large ports being opened and closed by the pistons were overcome by using rotary valves on the intake side, which necessitated the 26mm carbs sticking out of the sides of the engine.
A hefty four bearing crankshaft combined with forced lubrication from a separate oil tank under the seat takes care of the bottom end. Primary drive was by a set of helical gears which whined but showed no other sign of wear (any Triumph owner will revel in such sophistication). A still slick six speed gearbox was made interesting by the dry clutch which grabbed, shuddered and made expensive sounding noises. I consoled myself with the thought that there were a pile of spare clutch plates and drums available.
Despite its age I was most impressed with its smoothness and hard edged acceleration, a light drizzle of blue smoke accompanying the bike. The gear driven oil pump was controlled by a cable from the throttle, thus ensuring more oil was delivered when the revs were high. The yowl from the exhaust was the stuff from which dreams are wrought.
I was less impressed with the chassis, carrying as far as I could tell original suspension. Equipped with 19" wheels, shod with Venoms, stability was not too bad on a smooth road. But surface roughness completely messed up the machine's poise. At both ends the suspension was down on its stops and exhibited no signs of damping. The high, wide bars didn't help any, with only 370lbs to chuck around I soon found flat Vinnie type bars were much better suited to the chassis.
They helped take a bit of weight off the torso as well, the seat needing all the help it could find as it turned to a plank after much less than a 100 miles, which was a shame as the three and half gallon tank allowed a range of almost 200 miles. Wheelbase was almost identical to a Triumph 500 twin, weight similar, but distribution of that mass was distinctly different with the front end feeling very light. Not that I am of an age to indulge in wheelies. The seat height was low and the petrol tank very narrow, giving this 5'9" rider a feeling of security, both feet able to be planted firmly on the tarmac.
As a fan of British bikes I found one feature of the Bridgestone brilliant. The brake brackets were duplicated on both sides and the gearchange shaft stuck out each side of the engine. It was possible to have the back brake and gearchange set up as an old British bike or in the now more conventional mode. I suppose if you wanted to be really strange you could have two gear levers! I opted for brake on the left and gearchange on the right, luckily the kit for swapping the brake lever over was amongst the cache of spares.
The bike would scream up the ton in fifth, wallowing all over the road, then usually refuse to go any faster in sixth. Down very steep hills it was possible to put 110mph on the speedo. Vibration was conspicuous by its absence, although that might just be down to myself being used to old British bikes.
The gearbox had neutral at the bottom, which was quite a clever feature in that you could just keep stomping on the lever until it was found. On the other hand, if you lost count of which gear you were in, you could suddenly find yourself free-wheeling along in neutral when the extra bit of engine braking was desperately needed. To be fair to the bike, there was an idiot light that came on when the bike was in fifth, although until I was used to the nature of the beast the close ratio set-up of the gearbox caught me out a few times.
One thing the boxes of spares did not contain was a spare set of brake shoes. The Bridgestone comes with seven inch drums, the front TLS being on the edge of being down to its rivets. The result of such wear was that the brake never really had any great power and often faded away altogether. After frightening myself half to death for a year I finally conceded defeat by fitting a wheel and disc off an old Kawasaki KH250. This doesn't work any better in the wet but has transformed the safety factor in the dry.
Similarly, I hunted around the breakers for some better shocks....don't know what they came off but they stiffened up the rear end. Some variation in springing and damping was possible by relocating the shocks in an alternative position at the upper end - rather in the style of Velo's but without the range of adjustment. I had some springs that went into the forks with no trouble except that they were half an inch too short; fixed with a pile of washers. Doubtless Bimotas owners will be rolling around on the floor either in hysterics or horror.
The result on the road was rather more pleasant than I'd any right to expect. It still bounced around a bit over bumps but kept to the requisite line as well as the Tiger 100 I had in the garage. That was an interesting bike with which to compare the Bridgestone as they were of a similar era and price when new (now the Tiger was worth about five times as much). The Triumph could not accelerate any where near as well, vibrated horribly once past 5000 revs, was 5mph short on top speed and could not match the 350's 85-90mph cruising gaite. Most surprisingly, both machines averaged 60 to 65mpg.
The Bridgestone had several annoying faults. The spark plugs would only do 500 miles before refusing to start the machine until replaced. At least one carb a week would suddenly allow the petrol to flow out. The chain needed daily attention, refusing to last more than 4000 miles, although the sprockets looked like they were still original. Every other week the baffles had to be removed from the silencers to allow all the accumulated gunge to be cleaned out. The swinging arm pivot lacked support from the frame, consequently the bearings displayed a mind warping tendency to either wear rapidly or break up altogether. I had a dozen spare sets and went through four in a year!
The electrical system was twelve volts but idiosyncratic in nature, the lights flickering at a dangerously low illumination level at tickover, often blowing if you dared to encroach on the point of maximum power production at 7500rpm. They were not capable of illuminating unlit country roads. The ignition switch often needed a thump to make it work, although it never failed once the motor was started up. The kickstart was on the wrong side but even with a 9:1 compression ratio not much effort was required, usually starting on the second or third prod.
I've done 9000 miles on the machine with nothing major going wrong. Which is typical, I have enough engine spares to do about six rebuilds and the bits are just taking up space. Looking at the engine screws, the bottom half doesn't look like it's been touched. I've had the cylinder head and barrels off twice to clean off the carbon deposits, but the only sign of wear was a few marks on the bottom of the pistons.
For its time, the Bridgestone must have been a remarkable motorcycle. I think it must have been Kawasaki who bought the rights to the engine as it's very similar to their Avenger twin. It doesn't quite possess the wildness of their later triples, but if it was their inspiration I would not have been at all surprised. I find the 350 to have as much character as any British bike I've owned....it's my first serious Japanese bike and won't be my last!
Walter Blair