Thirty years of SUCCESS

Suzuki’s 250cc twins have been have been providing the basis of production and classic racing fun for more than 30 years. But were the Hamamatsu 250s ever capable of 100 mph in road trim? John Nutting delves into his records from MIRA.
AS runaway victor of this year’s 250cc Pre-TT Classic, Karl Hayes continued a reign of success for Suzuki two stroke twins that goes right back to their first introduction in the Sixties.
The Manxman might have had a few problems with blow-ups in practice but he managed to find enough parts from three engines to assemble a race winner on the Isle of Man’s southern road circuit at Billown.
Uncomplicated and durable, Suzuki’s two stroke twins have been staple racing tackle for more than three decades, even though the factory made few pukka production racers and even fewer 250cc works Grand Prix bikes. Until 1965, well-heeled learner riders looking for Japanese sophistication to blow off their mates’ big British twins had a choice of Yamaha’s fast but fragile YDS3 247cc two stroke (launched a year earlier) or Honda’s epochal overhead-camshaft CB250 twin that revved to more than 9000 rpm.
For the 250cc class, Suzuki had been making the plodding T10. But suddenly it all changed when the Super Six arrived - the same year that the Beatles released their Revolver album. The T20 had clean and stylish lines that echoed the race bikes but, more significantly, its rider had a six-speed gearbox to play with - and a rumoured ton-up top speed. For a 250 that was nothing less than phenomenal.
Suzuki’s UK importer saw the bike’s potential but quixotically it entered a team of three T20s in the 1965 International Six Days Trial. Highly strung, the bikes weren’t best suited to off-road use, one losing its sparks. But Cumbrian dealer Eddie Crooks, a Manx Grand Prix winner with Nortons, had seen the writing on the wall and bought the failed machine with the idea of entering the bike in the Isle of Man that September.
The T20 exceeded all expectations. Despite using a stock engine, Frank Whiteway took the Crooks Suzuki to 11th place in the 250cc Manx GP, averaging 82.45 mph. It was the start of a long association between Eddie Crooks and Suzuki twins that continues to this day.
It showed that although Yamaha offered capable off-the-shelf racing machines, Suzuki’s T20 ‘Super Six’ could easily turn its hand to production racing with TT honours and a class win in the Thruxton 500-miler when Stan Woods joined Whiteway.
Okay, so the bike was fast - but 100 mph for a fully-equipped 250cc road bike? We wanted to believe it as young impressionable riders, of course. And when I joined the weekly newspaper Motor Cycle in 1972 as a trainee writer and road tester I fostered the usual thoughts that Suzuki’s little twins were giant killers.
By then the T20 had been superseded in 1969 by the T250 Hustler with a smaller tank, more power but still retaining huge drum brakes. In 1970, the power was upped to 30 bhp at 7500 rpm and the bike renamed the T250-II, while in 1971 it became the T250R and in Europe the T250J.
I never found out just how quick the early Suzuki twins were. The bike was reaching the end of its model life. Suzuki launched a restyled range in 1973 that included the 380 and 550 aircooled triples and the 250 twin received similar treatment, including the ‘Ram Air’ cooling cowl over the cylinder head.
The GT250K looked much more substantial than the T250, with a bigger 3.3-gallon fuel tank, chunkier instruments and more bodywork below the beefed up seat. Visually, the biggest change was the adoption of a 10.75 inch diameter front disc brake.
Inside, the engine was largely unchanged. The crankshaft spun on three ball bearings and the mains and big ends were lubricated by oil fed from a separate tank, the metering to the bearings being controlled by engine speed and throttle opening.
The separate light-alloy cylinders had steel liners and simple piston porting using two transfers and a single exhaust. Bore and stroke were the classic 54 x 54mm to give 247cc. With bigger 26mm Mikuni carbs the power was upped to a claimed 31 bhp at 7000 rpm, much more than the original ‘100 mph’ Super Six. What could the GT250K manage?

Kawasaki's MAMMOTH

But unlike the prehistoric monster, the Z1300 in still with us. Winner in the power stakes when it was introduced at 120 bhp, fuel injection boosted that to 130 bhp. Bob Berry rides one of the last made. Pictures by Terry Joslin.
LATE in 1978, at the Cologne Show in Germany, Kawasaki unveiled the most powerful bike yet built and prompted a debate that led to the (short-lived) voluntary manufacturers’ agreement to limit power outputs to 125 bhp.
The colossal six cylinder, watercooled Z1300 came along just a year after Honda’s own ‘six’, the CBX. That had been awesome enough but the Zed boasted 15 more horses at 120 bhp!
Fierce debate in the bike press was already under way about just how far the Japanese could go in terms of power output and there were rumblings of government legislation unless something was done to curb the horsepower race between the Big Four. The voluntary 125 hp agreement was introduced in Britain to head the politicians off at the pass.
The Z1300 was powerful alright but the engine alone weighed more than a 125cc bike of the day. With its shaft drive and the six gallon tank filled with petrol it tipped the scales at a massive 660 lb.
I remember being distinctly unimpressed in Cologne that year, dismissing the huge thing as a dinosaur and never bothering to get around to riding one - the GS1000 Suzuki or Z650 Kawasaki being more to my taste at the time.
In fact, the GS1000 ran the Z13 very close in straight line speed and would leave it standing on the bendy bits. So what was the point? And how come its production run would carry on for ten years during which 20,000 were sold?
One-upmanship in the power race was probably the major factor but testers of the day enthused about the bike’s smooth power delivery and effortless 100 mph plus ‘cruising’ speeds - ironically, only acceptable on unrestricted autobahns in Germany, where the voluntary power limit was 100 bhp...
Like the magazine Superbike said in 1979, “As an exercise in corporate one-upmanship it’s a dazzling success, which isn’t altogether surprising considering that this is its raison d’etre. What is surprising is that, lurking under the tinsel and technology and almost secondary to this central purpose, is a surprisingly good heavyweight bike.”
Kawasaki had conceived the idea of the Z1300 back in 1973 and opted for watercooling and just two valves per cylinder to keep the engine relatively narrow. Three carburettors fed the cylinders, in contrast to the CBX’s angled bank of six.
There was nothing sophisticated about the frame - a conventional but substantially beefed-up version of the twin cradle designs of the day. Suspension was equally standard with sturdy air-assisted 41mm leading axle front forks and simple twin shocks at the rear.
Testers of the day reckoned it handled quite well for a bike of its size. Not a view shared by Dave Marsden of Z-Power (01942 262864) who was a parts manager for a Kawasaki dealer in those days.
“It handled quite well compared to a pig on stilts,” he said in his Mechanics Z-Files article in 1999. “Just what were those road testers on?”
As Dave reported, the Z1300 was not without its problems. Fork seals constantly leaked, front brake discs warped, the rear disc would seize and the rear shocks were virtually worn out after 2000 miles.
Debut ride SO what was in store for me as I headed for Bourne in Lincolnshire one sunny Sunday morning for a debut ride on Kawasaki’s mammoth? One comforting fact was that this bike was one of the very last Z1300s made with, hopefully, improvements to the problems highlighted by Mr. Marsden.
Many of the early faults were dealt with under Kawasaki warranty and at least in the suspension department this bike would have better forks and air shocks at the rear. Another big difference was that this bike featured fuel injection instead of carbs, introduced on the model in 1984. Fuel injection was said to raise the power to 130 hp.
Mechanics reader John Penney (we’ve tested some of his bikes before) contacted me last year with a offer of a ride but winter weather closed in and we postponed until a climactic improvement.
His bike is a Z-G1300, first registered in 1990 but built in 1989, its last model year. John, a police patrolman (in cars, not on bikes) bought the bike last July in Peterborough. It was up for sale for £4000 but he managed to get it for ‘substantially less’.
He is the third owner from new and toured the North Yorkshire Moors on it, loaded with luggage and his wife on the pillion. “It’s comfortable but not the best in corners,” he said. “But we did 1000 miles and the air shocks and forks made it feel like it was just wafting along.” The clock now shows just 11,600 miles.
John believes the later Z1300s were built in America and this might be borne out by the presence of a ‘cruise control’ button in the switchgear. All that horsepower and a button to stop you exceeding 55 mph. Bizarre...
Snapper Terry Joslin arrived and with the sun still shining - but showers forecast - we headed out of Bourne on the lovely stretch of road that is the A151 to the Corby Glen junction on the A1.
The fuel injection bikes have a ‘fast idle’ switch rather than a choke and as the 1300 warmed up I remarked that it didn’t tickover in the silky smooth way described in old road tests. Then again, it wasn’t yet warmed up and John assured me I’d notice the difference.
That 660 lb weight soon made itself apparent as I nervously negotiated the junctions around the housing estate to the main road. This would take some getting used to. In fairness, the shaft drive was very smooth, no trace of transmission snatch at all like on big v-twin Guzzis.
But at slow speeds like this on a bike I hadn’t ridden before (and someone else’s bike at that) I didn’t feel particularly confident about holding it up if I had to ‘take a dab’.
Initial wobbles behind me, we headed for the villages of Edenham and Grimsthorpe, the latter home to a superb castle. With clouds gathering we elected to get the riding shots done before I had the opportunity to get really acclimatised to the bike.
But it soon became apparent that this bike would not respond to too much ‘rider input’. Welting up to a corner as you crack down through the five-speed gearbox and then lay it in and accelerate around is wasted effort. That just appeared to get the front end wavering under all that power.

SCULPTED from a humble Honda Twin

Sculptor Jonathan Woolfenden had always liked the look of the Black Bomber tank. When he discovered it fitted his cheap CB500T runabout, he decided to create a motorcycling masterpiece.
FPREJUDICE is a terrible thing to admit to, but faced with a special based on the Honda CB500T, it is hard to deny. Despite their owners’ tender loving care, many one-off creations end up an incoherent mix of bolt on ‘goodies’.
Add to that perception one of the Seventies least loved bikes (as admitted by Neil Murray in his own Mechanics series about the bike) and the maxim ‘You can’t make a silk purse out of a sow’s ear’, springs to mind.
Jonathan Woolfenden, a sculptor, bought his 500T two years ago. “I needed a bike quickly to take my girlfriend away for the weekend,” he explains. “It was cheap at £275 and ready to go.”
With 23,000 on the clock it ran well so the decision to hang on to it wasn’t difficult and he set about looking for spares. The semi-derelict Honda 450 Black Bomber he got for £100 proved to be the catalyst for his creation.
“I loved the style of the Bomber,” he enthused, “and one day I tried the tank on the 500. It fitted, so I decided to make a stripped-out cafe racer like the classic racers in the USA.”
The first area for his attention was the handling, as he was determined this would not merely be a cosmetic exercise. Pinpointing the 500’s weakness - the poorly supported rear end - he welded in two extra frame tubes and two cross bars to the rear subframe. The standard of work is so high it shames the original factory efforts.
“I found a box-section Laverda swinging arm,” adds Jonathan. “It needed drilling out at the pivot and the rear spindle. Oh, and it required new shock mounts welding on and I had to make chain adjusters from scratch.”
He makes it sound simple but this single-minded drive for the best and neatest solution has resulted in a modification that looks a naturally integrated part of the bike. Sebac rear shocks, a £25 autojumble find, finish off the rear end.
At the front, he dropped the yokes just over an inch down the forks - another racing mod - and fitted clip-on handlebars. “The extra weight helps directional stability but slows the steering a little,” he says. An £80 steering damper eliminates any final unwanted oscillations.
Breakers to the rescue
THE front brake’s future was decided when he found the correct-sized double discs, ready drilled, in a box of bits at his local breakers. The fork legs both had mounting lugs so drilling his discs to match, he fitted a CB750 master cylinder and Goodridge hoses, reversing the calipers while he was at it.
The rear drum brake is standard but has been changed to cable operation as a result of fitting rear-set footrests. The brake is not as sharp as before and is on the list for more attention. The rear-sets themselves were created from a £10 pile of mis-matched pieces, the gear linkage being fabricated from bits of a JCB crane control, welded up to suit.
The engine is standard internally but the CV carbs have been junked as these are often blamed for the standard 500’s snatchy low speed performance. “I fitted Mk 2 36mm concentrics with velocity stacks,” he says, “because they are easy to tune and modify. The bike revs more freely and cleanly with them on.”
Again, this mod has been used successfully in racing and leaves the torquey feel of the 500 unchanged. The fuel comes from the Bomber tank via a Norton big-bore tap to cope with the demands of the carbs.
The exhaust is another racing fabrication. The down pipes were made by Swarbrick Racing and have a larger bore than the originals. At £60, including new collars, a bit of a bargain. The reverse cone meggas came from Unity Equipe. At this point the only thing left cluttering up the looks of the bike were the battery and the wiring. Once more, the neatest solution was chosen and everything was moved under a new seat unit. A sheet steel mould was made for the hump and a fibreglass copy taken from it.
The frame rails were cut down, a seat made from scratch and the whole lot mounted on quickly-detachable lugs for ease of access. All the electrics are now safely out of sight and a doddle to work on. The unreliable electric starter has been removed and the hole blanked off.
The headlamp shell is of uncertain parentage but has more than a hint of MZ about it. The actual headlight is a Suzuki item. Mounted on the headlamp is a Kawasaki KH250 rev counter and the CB500’s speedo. The rear light is from a trials bike mounted on the Bomber’s cut-down Bomber bracket.
Even the finishing details are neat - the dog-leg levers in polished alloy and the Manx Norton blade mudguard on hand shaped mounts secured by tiny stainless Allen bolts.
“I tried to make something that looked period that could even have come from the factory,” said Jonathan. He has probably succeeded - but how does it go?
Open road bike
THE bike is not set up for town work so Jonathan rode it out of Manchester’s congested city centre with me following on his restored Black Bomber. (He’s a busy lad.)
The first impression was of the sound, a fruity bellow, the like of which is rarely heard in these sanitised times. At traffic lights the pulses from the meggas gently massaged my face and gave a farewell slap as the 500 accelerated away.