Love at first sight, Elsie meets Suzy
The formula for any truly great sporting machine is an easy one to concoct. The secret is to not over egg the pudding, simply use a light and agile chassis allied to an easy to use engine, all held to the tarmac by good handling and sweet manners. This is all present and correct in a well assembled Yammagamma, the original chassis being little more than a scaled down GSX-R frame and cycle parts, while being 20% stiffer, and around 30% lighter, than the old style Yamaha steel tubed frame.
The transplant isn’t a hard one either, the space within the RG250’s frame tubes is bang on for the Yam lump and, all that is needed engineering wise is a few easily fabricated brackets and spacers before the power valve engine can be securely bolted in. The result is factory built look with just the extreme curve of the hose from the water pump to the lower radiator coupling giving the game away. The Yamaha engine sits in the chassis as if made for the task, while all of the ancillary parts fit without looking out of place too. Even the YPVS exhausts fit a treat, making the finished article look every bit the factory-produced machine it could easily be.
The creation of the Yammagamma is a natural progression for the RD350 YPVS engine, effectively finishing off the work Yamaha never started, the original machine hardly moving on during the decade of its existence sticking firmly with technology either borrowed from the 70’s or built to strict budget requirements. Quite why the tuning fork brand never saw fit to create such a beast one will never know, as the engine was already in existence and ripe for further development, and it’s a safe bet that it would have been far more successful than the underpowered and overweight RD500LC. Of course, Yamaha, along with the rest of the Jap brigade, did create some stunning quarter-litre machines as the 80’s wrapped up and the 90’s unfolded, but those in the know appreciate that there is rarely a substitute for capacity and, on the road at least, a 350cc engine will always feel far stronger than a 250cc one, even if the latter does produce stunning levels of horsepower. It’s that big punch that the 64mm pistons give, over and above items with a draft 100cc less, that does it. The two massive kicks every time the crank rotates adds up to impressive torque and horsepower levels that, once liberated from the heavyweight Yam tube work, really starts to make an impression.
In the Suzuki framework the Yam engine lifts it skirt and takes off with an enthusiasm rarely seen, always begging to be let off the leash and allowed to play. Wheelies are easy in the lower three gears while nipping up the ton and back is a doddle, rapidly accelerating through the six ratios as if they are a close ratio box, the Yam gearbox never before feeling so light and keen.
Handling is correspondingly fast, way faster than the sharpest of LC’s, feeling much more like a thoroughbred race machine, which is effectively what the Yammagamma is. With nearly double the power, with no significant gains in weight or size the transformation is stunning. The increase in performance is hardly surprising, the Yamaha engine easily out doing the quarter litre Suzuki, whether it be the factories wild “PR hype” claims of horse power or the harsh reality once the RG is placed on an honest UK dyno, the Yamaha, even in standard trim, has the upper hand by a huge amount. The power valve engine has torque by the bucket load, easily driveable from way down in the rev range but that isn’t where the fun is, far better to get the twin up on to the pipe and go hunt some big meat. Keep away from lengthy straights and few would hold a candle to a well-ridden Yammagamma, even modern day plastic rockets will struggle in a B-road fist fight, the Yam engine throwing the Suzuki chassis like a terrier killing a rat.
With no weight to haul up, the weedy looking Suzuki brakes have little to push them into overload, they maintain great feel and stopping power, even when used repeatedly. The hydraulically operated anti dive working surprisingly well too, being based upon the system used to great effect on the World Championship winning RG500 race machines of 1981-82. The forks do stiffen up nicely, in proportion to the braking effort, without going solid and losing all feel from the front end, a task so many of these systems from the early 80’s fail to achieve. This is the same for the rest of the chassis too, feeling as if the box section alloy could handle far more power and, with it, acceleration and speed too. This shouldn’t be a problem as the YPVS engine can be made to produce reliable horse power figures way up into the high 80’s in the right hands. Some Yammagamma builders ambitiously opt for later suspension and forks, many preferring the upside down route, but this can only be for purely cosmetic reasons, as the original formula works so well it is hard to see where any improvements could be found or made. There is always the danger of going too far with this approach and ending up with a machine too heavy or too complex to be as effective, the original Yammagamma is a simple beast
On the whole its like the Yammagamma is having a laugh, as if the chassis is constantly challenging the engine to do more and vice versa. It’s a great double act and one that doesn’t come along too often, a mixing of manufacturers best products with supreme success.
How did it all begin?
The story starts back in 1983 just as the worlds press where raving about the latest pocket rocket the Suzuki RG250, the alloy chassis and peaky stroker engine raising many a journo’s heart rate at the types launch. This prompted ace tuner Stan Stephens to buy one, the first new machine he had ever bought. As time rolled on Stan realised that the hype surrounding the Suzook was largely viewed through rose tinted specs and in turn written about in adjective frenzy, the press bikes clearly having been highly prepped and tuned, and in reality the RG in the flesh was a shadow of the legend surrounding it.
The engine proved to be fragile too, the dated LC 250 still proving faster and more reliable than the Suzuki, so the next step was obvious if at all possible. The Suzuki chassis was light years ahead of anything Yamaha had built to date so, why not put an LC mill in to replace the Suzuki engine? It looked entirely feasible and once the RG engine was freed from it’s over handling framework it became clear the Yam engine would virtually slot straight in. If this was the case then why not opt for 350cc engine instead of the 250 and, while we are at it go for the latest power valve equipped version too. The result was the first Yammagamma, a machine that could see off most road going machines with its heady mix of sweet sharp handling and almost double the power of the original machine.
Stan Stephens built around 20 complete Yammagamma machines, some for the track where, of course, they excelled, but most where destined for the road. The success of the design led to a whole raft of after market exhausts and tuning mods that would see the 350 YPVS and LC series live on as high performance machines well past their intended sell by date. Many more Yam/Suzook hybrids have since seen the light of day, the whole process being relatively cheap and easy to carry out and the result, a stunning giant killer with an enviable cult status.
How to build a Yammagamma
The whole conversion is a relatively simple one with little in the way of cutting or fabricating being necessary. The engine mounts line up with an uncanny accuracy, with just a set of new engine plates needed for the rear and two spacers for the front, to get the power plant bolted up, almost as if the Yam engine was destined to live in the Suzuki frame from the outset. It is also fairly easy to either use the YPVS wiring loom or with a bit of patience and electrical know how cross-reference the wire colours so the Yamaha stator and ignition will power the Suzuki items.
Most builders opt for the former when it comes to the wiring and soon find that the complete Yamaha loom switches etc can be transplanted, the YPVS tacho fits neatly into the space left by the Suzuki item and the steering lock works too if the ignition switch is aligned correctly. There is some internal space issues, finding somewhere to mount the extra bits needed for the power valve motor etc, but careful planning or the odd bit of wiring extension, will overcome most of these problems. The only down fall would appear to be the reverse gear shift pattern caused by having to use of the Suzuki gear lever the wrong way around. Of course for the racers out there this isn’t a problem, but it does take some getting used to for the road rider.
Suzuki RG250 Timeline
1983 Suzuki RG250 D GJ12A-106347 – The original format Mk1 RG was released in this March of this year, on paper a real stunner but in real life fragile and fickle. It was the first production machine to feature an alloy chassis.
1984 Suzuki RG250 E GJ12A-134997 – the MKII RG saw up-rated front brakes, now using 4-piston calipers from the GSX-R400, and minor cosmetic changes.
1985 Suzuki RG250 F GJ12A-164237 – New shape fairing and 30mm shorter wheelbase for this RG.
1986 Suzuki RG250 G GJ12B-104823 – Available with a full fairing as an optional extra once again the wheelbase shrinks by a further 20mm.
1987 Suzuki RG250 H GJ12B-145623 – The last year of the RG, although surprisingly, also the one that saw the most significant modifications. The front forks grew by 2mm to 38mm while the rear wheel got both wider and smaller in diameter too, now wearing a 120 section 17-inch tyre. The front brake discs grew in diameter by 10mm too.
1988 Suzuki RGV250J – The first of the V twins, faster, lighter and more powerful than all before it,
no need to be slotting Yamaha engines into this baby then?
Yammagamma MkII Specifications (YPVS in parenthesis were relevant)
- Engine liquid cooled, 2-stroke, parallel-twin, YPVS exhaust control
- Capacity 347cc
- Bore & stroke 64mm x 54mm
- Compression Ratio 6.0:1
- Carburetion 2 x 26mm Mikuni
- Max Power 59bhp @ 9200rpm
- Torque 34.2ft-lb @ 8500rpm
- Ignition Hitachi CDI
- Transmission 6-speed, chain final drive
- Frame box section, alloy tube
- Suspension 36mm anti-dive forks
- Full-Floater rear suspension
- Wheels 100/90 x 16 110/80 x 18
- Brakes 260mm discs, 4-piston calipers, 210mm disc, 2-piston caliper
- Wheelbase 1355 mm ( YPVS 1385mm)
- Weight 130kgs (YPVS 174kgs )
- Fuel capacity 17 ltrs (YPVS 20ltrs)
- Top speed 135mph (estimated)