 The Two-Stroke Shop
Stephen Rothwell and Wayne Wright
www.twostrokeshop.com Email: info@twostrokeshop.com
9 Compass Cl, Edge Hill
Cairns, Queensland 4870
Australia
Land Tel. (In Australia): 07 4032 1708
Land Tel. (Outside Australia): +61 7 4032 1708
Mobile Tel. (In Australia): 0427 774 285
Mobile Tel. (Outside Australia): +61 427 774 285
TSS500 Engines – Features and Benefits
TSS500 Engines – Features and Benefits
 The TSS500GP Cylinder
is THE most advanced high-performance two-stroke motorcycle engine on the market today. At its heart is proven alloy monoblock, Nikasil-plated Cheetah cylinder technology, with porting specifically engineered for the application - which is to say making hugely thrilling Street and Race Two-Stroke Superbikes.
GP-Proven Curved Power-Valve Blades
This new generation of powerful yet flexible two-stroke engines utilise a revolutionary Grand-Prix developed curved power-valve blade, that follows the curve of the piston more closely and accurately than flat power-valve blades are able to.
This innovation alone provides a significant boost in low and midrange power and torque.
This enhancement is typical of The Two-Stroke Shop's attention to detail, and commitment to bringing you the most effective two-stroke technologies.
YPVS-Hybrid Servo-Operated Blade Power-Valves
We tested the Cheetah's exhaust pressure-operated power-valves and found they lack the precise graduation of operation required for motorcycle use. Simply, they lack finesse at crucial part-throttle running; the blade type valves tending to snap shut when off the throttle and snap open after the throttle is opened; resulting in sudden unwanted 'turbo lag' like blasts of power that may result in highsides.
Accordingly TSS has developed a hybrid blade-type power-valve system that utilises Yamaha's own RPM-defined YPVS servo-driven system. The result is a seamless integration of both systems, boosting torque and power down low while allowing for generous port maps - and a massive top-end kick.
The TSS500GP cylinder is designed to work in concert with our own straight-shot intake manifolds, and TSS modified Keihin FCR carburettors. Once again, these are optimised elements; each of which contributes to a beautifully-balanced and very much on-song engine that develops 112HP @ 9800RPM. Every detail of this engine has been optimised by our Grand Prix and Championship-winning engineer.
The TSS500LC Cylinder
 Like the original Yamaha RD350LC, the TSS500LC is sans power-valves, making for a classic razor-sharp two-stroke powerband hit, hoisting up the front wheel with a banzai spirit Yamaha engineers would be proud of.
The LC cylinder utilises a slightly more tractable port map than the GP variant; making slightly less power (100HP) than its GP stablemate, albeit with a more noticeable rush of power when coming onto the pipe.
The 500LC cylinder is real forbidden hooligan fruit - it makes every ride a mile-wide smile. Subtlety is not an option.
If it's an abrupt crack of two-stroke oomph you're after, the TSS500LC will most definitely delight.
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Crankshaft:
TSS500LC and TSS500GP Balanced Crankshafts: Forget generic +4mm stroker cranks, and finger-numbing vibes. Our balance factor-corrected 58mm stroke crankshaft is balanced to precisely match the TSS500 motor’s 73mm forged Wossner pistons. Nothing else will do, quite frankly. Race engines get balanced cranks, and we believe your engine deserves this treatment too. All the fun, all the power, and silky-smooth as you go. This is achieved by precise machining of crank webs to achieve the required balance factors.
Benefits:
(1): A smoother-running engine at all revs, with no intrusive resonant vibes.
(2): Less stress on crank = Longer crank life
(3): Enhanced high-rpm running/power (less vibration = less resistance = more horsepower.)
(4): Comfort on long road rides, and better ‘feel’ of controls when racing = less fatigue - more enjoyment.
 TSS500LC and TSS500GP Crank Layout Options
Further, we are offering our cranks in a choice of 180° or 90° firing orders. The 90° layout in a parallel-twin offers a reduction of peak rocking-couple forces of 31%, which is one of the reasons why KTM’s Technical Director Harald Bartol has chosen this layout for his team’s 250 FRR GP bike.
The diagram below shows a 180° crank layout in the black trace and a 90° layout in the red trace. Here the lower rocking-couple peak forces inherent in the 90° layout can clearly be seen.
Please note that the Rocking-Couple Peak Forces are independent of the crank’s Balance Factor. The Balance Factor is all about balancing the crank assembly precisely to match the reciprocating components, i.e. the piston/pin/rod etc, whereas the Rocking Couple relates to, in the case of a 180° parallel twin, the violent oscillation of the engine to the left and then to the right as opposing pistons reach TDC and BDC simultaneously.
 Whereas, in a 90° crank configuration, a higher inertial momentum (flywheel effect) can be maintained about the crankshaft by having one piston always at or near maximum velocity while the other one comes to a ‘stop’ and then changes direction. The pistons are never both ‘stationary’ at the same time.
This ‘flywheel effect’ also allows the use of smaller actual flywheels.
Therefore a 90° layout will always give the crank an easier life, and accordingly crank life will be extended. This is particularly important for racing applications.
TSS500LC and TSS500GP Cylinder Head Inserts:
 Our billet head inserts ('head domes' is really ATV-speak - 'Head Inserts' is more the motorcycle road-racing nomenclature) feature state-of-the-art Toroidal Chambers, which are designed to suppress detonation; boosting peak power and allowing safer over-rev power.
Toroidal head inserts also bring spark plugs down lower in the combustion chamber, closer to where they need to be.
Integrated YPVS/Blade Power-Valve System
(TSS500GP Version Only:)
 Pneumatically-operated power-valves are OK for rough and ragged riding, as in the snowmobile/ATV/jet-ski applications they are most commonly used. At wide open throttle, exhaust pressure lifts the blade-type power-valves, effectively raising the exhaust port for high-rpm action.
But the problem with this type of power-valve actuation for motorcycle use is that as soon as exhaust pressure drops - for instance, when rolling off the throttle when approaching a corner - so does the power-valve. So, when the throttle is rolled on again to power off the turn, the power-valve is in its lower position, and there is a 'lag', similar to turbo lag, until exhaust pressure has built up and raised the gate once again. This is more than a mere inconvenience for the motorcyclist, because the rapidly-rising power-valve will unleash masses of abrupt horsepower when it is least expected, and highsides may well result.
We have developed a hybrid power-valve actuation system that utilises the Yamaha Power Valve System (YPVS) servo motor, coupled to a mechanism that raises and lowers the blade-type power-valve of the Cheetah engine. In such a way, we are able to control the power-valves as we need to - according to the RPM of the engine.
The result is seamless power-valve operation; with the blade always exactly where it needs to be at any given RPM.
TSS500LC and TSS500GP Straight-Shot
Reed Blocks/Intake Rubbers:
 We have designed ultra-short, straight-shot downdraught billet intake manifolds and intake rubbers with precisely the right section for optimum intake velocity.
The optimised round-to-oval shape transition in the CNC manifold block going into the reed cavity is worth 3HP alone.
Plus, the straight intake rubber boosts power by 5%.
These items the Cheetah engine was simply begging for. The ATV crowd tends to simply fit the biggest manifolds/reed blocks they can get a hold of ... wrong move. Intake velocity has to be kept high as it hits ...
TSS500LC and TSS500GP Custom Reed Valves:
 Again, a custom design from Moto Tassinari, the producers of V-Force reeds. Reed stuffers are matched precisely to the intake manifolds/carbs/entire inlet tract. Reed petals are of a custom thickness, for exactly the characteristics we require.
TSS500GP Carburettors:  This is yet another area where we have refused to compromise. We have adapted Keihin FCR semi-downdraught carburettors for two-stroke use; employing custom emulsion tubes and jets to this most high-tech, free-breathing carburettor. The FCR carbs are designed to be run with the intake tract up at around 30 degrees from vertical i.e. no 45 degree bend in the intake as per the "stock" manifold rubbers.
The FCRs also have more "adjustability" in the fuel/air circuits, making them harder to tune spot on but ultimately, a more accurate metering device.
TSS500LC and TSS500GP Pistons:
 All pistons are specially-ordered flat-top lightweight 73mm units from Wossner.
TSS500LC and TSS500GP Ignition Systems: 
A custom-designed, fully-programmable twin DC/DC - CDI ignition unit by Ignitech with programmable parameters for ignition timing; power-valve control; electronic power-jet control and throttle position system (TPS.) This is a twin ignition coil system that does away with the dreaded 'wasted spark' system, enabling each cylinder’s firing event to be timed independently of the other; freeing-up ignition timing options beyond the stock Yamaha 180 degree timing layout; making possible 90 degree crank firing layouts.
This new TSS ignition setup is generations more advanced than anything else on the market, reflecting our focus on providing the very best engineering solutions for all our engines.
Pipes:  Need we say more. Pipes have been designed by the Pipe-Meister himself - 500 GP pipe-builder Wayne 'Wobbly' Wright. Pipes are available for common fitments, i.e. RD-LC, RD/RZ YPVS, and of course Aprilia RS250/RGV250. Pipe options for the 485 engine will include welded sectional pipes and, for much greater affordability, die-stamped pipes. (Ideal for the hurly-burly of racing; a lot cheaper to replace.)
We will keep you closely advised on final pricing and specs; we plan to offer an introductory champagne-corking deal. Save those pennies! :-) Further details will also be uploaded to our website.
The Two-Stroke Shop
Stephen Rothwell and Wayne Wright
www.twostrokeshop.com
info@twostrokeshop.com
9 Compass Cl, Edge Hill
Cairns, Queensland 4870
Australia
Land Tel. (In Australia): 07 4032 1708
Land Tel. (Outside Australia): +61 7 4032 1708
Mobile Tel. (In Australia): 0427 774 285
Mobile Tel. (Outside Australia): +61 427 774 285
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TSS Custom Reed Valves
