Ton up Teenagers
There have been many races throughout the 20th century, but rarely one more hotly contested than the rush to get a quarter-litre road machine past the magical 100mph barrier. From the late 60’s on, many claimed to have achieved this feat, but the first genuine ton-up machine came a decade later.
The X7 was an all new concept, albeit a development of a design that had been around for 12 years or so, the air-cooled twin of 1979 playing safe in the chassis department choosing instead to make great weight savings in the power plant. This lack of weight helping the 28 or so gee gees to push the machine up to and often beyond the 100mph barrier.
The X7 is a tiny machine, comparable with a modern day 125cc bike and, with its size and economical build, comes a feeling of flimsiness. This doesn’t make itself know at road legal speeds but start to push the outer envelope of this 250’s performance, and its time to take a firm hold of the reins and enjoy the ride. The X7 wasn’t around long and as such finding one can be a tough call, they do stand out in a crowd how ever and anyone who was riding during the period, or shortly afterwards, will have a soft spot for one
The majority of failings with this machine are the effects of age upon the bodywork and metal, rather than mechanical woes. The attempts by the Suzuki design team at making a lightweight racer on the road does show many years on, the flimsy metalwork giving in to the corrosion and rust. The petrol tank can and will fail, either from the inside out or outside in, particularly around the seams of the lower edges, requiring the application of f internal sealant. Cosmetically the X7 doesn’t wear well, the seat soon gives up the ghost and tears along the indents that make up the pattern which then allow the moisture in and under the foam soon turning the metal base plate into rust.
The engine, being based on over a decade and a half of development work, is, as you would imagine, well sorted. The usual two-stroke rattles and knocks are easily fixed, any machine with over 20,000 miles showing on the clock will need attention to the crank and bottom end. Genuine pistons are good for around two thirds of that mileage, as indeed are the rings if good quality oil is used at all times. Any sizeable increase in power will see the clutch start to slip, this tiny unit, pared down in an effort to save weight and size, is at it limits of performance with a well set up engine in standard trim, so increases in both power and torque will soon have the plates complaining.
A short prod on the kick start soon has the perky twin bursting into life, running fluffy at first until the top end warms but, as the blue smoke lessens, and the rings expand to fill their gaps in the cylinder, every pump of the throttle has a sharper impact upon the revs. Click into gear and, with a smooth clutch hand gently introducing the engine to the rear wheel, it soon becomes clear that even with a set of reed valves to control the inlet tract the engine is quite peaky. When the engine is within its correct operating range the pull is strong, easily as powerful as any other two-stroke air-cooled twin but feeling much more so thanks to the lightweight and flighty chassis. It is crucial to keep the revs up around or above 5500rpm at all times when pulling away, the engine will drop out of its power without warning requiring a deft pull of the clutch lever to get the crank spinning up and the twin in its power band again. At speed, handling crosses over from the light and easy to move around to flighty, and verging on the dangerous. The extensive weight saving efforts have resulted in a machine barely able to stay on the road, while its short 1310mm wheelbase adds little to the straight line stability. The chassis is the only true failing of the design, hit a few closely spaced bumps, at anything like high speed and the bike loses all composure, bars flapping around, seemingly unconnected to the forks while the rear follows suit, leaving bike and rider looking as if they are trying to disco dance.
Despite appearing a shade dated in the braking department, with a simple drum brake at the rear and tiny disc, and a floating single-piston caliper up front, the Suzuki does stop without stressing the pulse rate. The rear drum is if anything too powerful and will lock the rear wheel at any pint in the bikes speed range, thankfully the front doesn’t echo this behaviour, the balance is just about right hauling the bike up but never threatening to stop the front tyre from gripping the tarmac. The X7 is a culture shock, this is how it was done back in the late 70’s and as such much of what it does would not be acceptable in today’s society. It should carry a health warning about speeds above 70mph, as any kind of rough surface has the bike doing it own thing with you the rider simply sat awaiting its return to normal service. Of course get the bike on a billiard table like race track and you could ride it around, way above road legal speeds, all day and many did, after all, the X7 was the bike to have during its brief period of dominance before the LC arrived on 1980.
On the road however and the Yamaha RD250 has it in the bag by a good margin, there being hardly a fag paper in it speed wise, but a good deal more in the handling department enabling the RD to carry on when the Suzook is looking for the hedge bottom and struggling to keep up.
Suzuki GT250 X7 Model history
During the latter part of the 70’s Suzuki was losing in the performance and sales stakes while Yamaha were winning year after year. The RD250 in its various forms just had everything the 17-year-old biker needed, the looks, the speed, and above all bags of kudos thanks to Yamahas successes on the race track allied to significant, year on year, up dates. The answer came in the form of the GT250 X7, no doubt the name was chosen as a nod to the past, as the last machine to have a hold on the 100mph barrier was the Suzuki X6 of 1965.
The X7 can still trace its family tree all the way back 60s, with only minor technical advancements setting it apart from the rest of the GT 250 and 350 range. Much work was done to save weight, the complete bike is 25lbs lighter than the GT250 C it replaced, the engine alone weighs in around 16lbs lighter than its predecessor and is a good deal narrower too. The width was reduced thanks to the narrow spacing of the barrels, Suzuki 250cc twins of old had to share a common bottom end with the 350 version, but, with that model long gone from the line up, it just left a pair of 54mm bores to accommodate so the size could be minimised. To get more gas into the engine a mix of crank case reed valve induction and the more traditional piston port was devised, this allowed a smaller inlet port to be used in the rear of the cylinder reducing both piston wear and excessive mechanical noise. The reed valve feeds the bottom end of the engine, a feature already used to great effect on many Suzuki off road machines, opening at the same time as the piston operated port and closing slightly before it, but increasing the mid range power and torque to levels not achievable by piston port alone.
The styling had to be angular and purposeful looking, although the commuter market was not completely forgotten in favour of the teenage learner buyer and the bike was made to be approachable to a wide variety of rider not just the racer on the road. Early designs featured a monoshock rear end but this was dropped as it steered a shade too close to the Yamaha way of doing things, what did stay throughout the design process was the racey looks.
Suzuki GT250 X7 Specifications
- Engine – air-cooled twin-cylinder two-stroke
- Capacity – 247cc
- Bore/stroke – 54 x 54 mm
- Power – 28.5bhp @ 8300rpm
- Torque – 18.9ft-lb @ 7500rpm
- Carburetion – 26mm Mikuni
- Transmission – 6-speed chain final drive
- Frame – steel single down tube cradle
- Suspension – 32mm telescopic forks. Twin shock adjustable spring pre load
- Brakes – 250mm disc single-piston floating-caliper. 175mm disc single-leading-shoe drum
- Wheels – 300 x 18 3.50 x 18
- Weight – 128kgs
- Top speed – 100mph
- Wheelbase – 1310mm
- Fuel capacity – 14.8ltrs
Suzuki X7 Timeline
1977 GT250 C
The last of the heavy and by now outdate GT range.
May 1978 saw the launch of the all-new X7. the bike was in instant hit although test soon revealed that the speed claims were on the optimistic side.
Minor cosmetic changes were all that was deemed necessary to keep the market interested in the X7, of course Yamaha knew different as the LC lay in wait, just around the corner.
Now updated with the clocks and square indicators in the style of the GSX250.
Suzuki took a sabbatical from two-stroke 250cc production and returned the following year with the radical, yet fragile liquid-cooled 250 Gamma.
Suzuki GT250 X7 Gallery
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