A few penny's dropping over at KTM...
This was a really good read given how alot of people think the PDS feeds shocks directly into the frame. The new frame has made it to the new SX(F) and XC(F) bikes but not the EXC/XC-W range yet...
Compared to our previous SX frames the 2011 frame design provides higher torsional and reduced longitudinal stiffness [the whole reason the japanese went to alloy frames] . In addition it is designed to absorb energy created from the rear wheel impacts. This new design benefits both the PDS of the new two-strokes and Pro-Lever linkage rear suspension of the four-strokes. The basic frame designs are pretty much the same. The main difference between PDS and linkage is the tower of the upper shock mount, which for both systems, takes the main role to isolate the shock absorber forces from the frame.
KTM has proven that the PDS rear suspension system is capable of winning any motocross race. But ,when it comes to Supercross, the PDS becomes more critical in regards to bike set-up. KTM's new linkage provides a better solution to the increased loading demands that extreme Supercross requires and covers a wider range of circuits.
Both systems have a certain rising rate, which means that when the rear wheel moves at a constant rate, the rate of the shock shaft increases, or in other terms, if the rear wheel travels at a constant velocity, the shock shaft is accelerating. The difference between the two systems is with PDS the shaft velocity does not increase as much as with linkage. The PDS system creates additional damping with internal systems in the shock, and as a result, both the linkage and PDS system produce similar dampening characteristics. The main difference lies in the fact that the PDS system provides a more linear spring progression than the linkage system. The PDS character is extremely beneficial for the lighter two-stroke bikes and to offroad applications, whereas a high-spring progression in the linkage system benefits the extreme Motocross and Supercross applications.
PDS 2011: Longer PDS shock to offer an improved rising-rate character.
Linkage: Completely new WP unit with piston and bushings that provide better seal and friction properties to handle the higher shaft velocities.
Both shocks also have a new spring retention and preload system to allow for preload adjustment without the use of hammer and punch. A wide range of adjustability of rebound and high/-low speed compression damping are KTM standard anyway.
Why PDS for the two-strokes?
The directly linked PDS shock has turned out to be the best solution for the two-strokes. Two-Strokes have a totally different engine characteristic than four-strokes and also a different centre of gravity. Many tests have proven that the PDS rear suspension fits better to the lighter and more nervous characteristics of the two-strokes. With the lighter PDS system, the two-strokes will keep a major weight benefit, also in the future.
There are new, cast aluminum swingarms for both the PDS and the linkage-equipped bikes. The single-component casting process allows unlimited geometry solutions and eliminates any inconsistencies created by welding. Updated mounting positions, higher profiles and optimized flex are supporting the frame and suspension characteristics.
All SX models are fitted with the latest generation of 48 mm USD front forks ?made by WP in Austria.? Due to intense development in the recent years the ?WP closed cartridge technology? has been fine-tuned for excellent sensitivity and damping characteristics, which has been proven in many shootouts of the last season. For MY 2011 new settings for each model match perfectly the needs of new chassis packages. Due to an internal closed damping cartridge these forks create more consistent damping characteristics in extreme use situations than open cartridge systems.
The KTM patented SX triple clamps can be called "works of art.? CNC-machined out of high quality aluminum billet, the sophisticated design and clamping system avoids squeezing of the tubes, while supporting the fork's action. In addition, the design provides a certain flex, which allows the triple clamps to follow the fork legs when deflected during hard landing or braking.
According to KTM's philosophy, "design follows function." Thus the KTM engineers put highest priority on rider ergonomics. And, in this respect, Stefan Everts took a key roll during the entire development process. Who could know the needs of a motocrosser better than a ten-time Motocross World Champion? From the first clay model till the final product Stefan was heavily involved with each step of the development and he really pushed the design team of Kiska until every single detail was addressed in order to get the ideal shape of a future champions bike. The results are super slim ergonomics and a bodywork with excellent contact points between rider and machine. He also insisted on having a wider and 50 mm longer rear fender. And not to forget features like the no-tools access to the air filter or the incorporated lift handle in the outer rear fender, which is well protected against dirt from the rear wheel.
The new layout of the airbox was driven by two main functions: optimised protection for the air filter against dirt and a maximum airflow for maximum performance. Due to the special design between filter and intake throttle body, the airbox was designed separately for every displacement and improves the power significantly. The ability to change the large Twin-Air filter quickly and without tools is the KTM standard and outstanding in the motocross world.
Weight reduced high-quality wheels with CNC-machined hubs and high-end Excel rims are hard to beat. They are the standard in terms of durability.
New silver rims not only appear lighter, they also take the unavoidable damages during tire changes much better than rims coated in any other color. Spokes are now covered with a noble zinc/nickel coating which not only suits the silver rims optically, but also has an improvement regarding corrosion resistance. New nipples made of high-strength aluminum the weight could be reduced again, which is an important feature supporting suspension action and easy handling.
The four-strokes have new improved silencers that score points with a modern and voluminous profile not only optically but also reducing the noise level to future noise emission regulations (115dB for the two-meter Max test). A bigger outlet diameter improves the performance and delivers a sound improvement.
New silencers for two-stroke bikes introduce a new ?two-component? technology. A strong plastic holder is injection-molded around the aluminium housing to attach the silencer to the motorcycle better.
The proven integrated cooling system routes from the cylinder head through the
frame triangle directly to the radiators, the removed tubing simplifies the radiator mounting and improves the air flow through the radiators. A new T-connector with an optimised fluid flow improves the heat dissipation.
The slim 7.5-liter tank made from lightweight polyethylene includes a compact fuel pump on the 250 and 350SXF models. All other models introduce a new fuel tank with the same capacity as well. The well proven ?-turn fuel cap allows easy and quick refilling and includes a security against unwanted turning.
Brakes by Brembo are serial equipment of KTM models and are combined with lightweight wave rotors which are the benchmark when it comes to feel and brake performance.
Other equipment ? highest level
There are many features on the new SX which highlight the KTM at first appearance against its competitors. For example, the comfortable hydraulic clutch, tapered Renthal handlebar or CNC-machined triple clamps, Twin Air air filter, high grade chain and sprockets, Also smaller details like foot brake lever with a high quality bearing
Ultra-compact four-stroke engine with modern electronic fuel injection and electric start. The extremely short stroke 349.5cc DOHC engine with 57.5mm stroke and 88mm bore has a very wide usable speed range, top performance and very efficient rideability. The layout of the 350 engine is close to the 250SXF engine and has bigger dimensions at nearly the same weight. The playful handling (similar to a 250 engine) results mainly from reducing the rotational masses to a minimum.
DOHC cylinder Head
Four ultra-lightweight titanium valves in combination with DLC-coated finger followers allow a high rpm limit of 13,000 rpm. Herewith the engine can deliver enough power to win every holeshot.
The crankshaft turns an intermediate gear, which drives the cam chain and at the same time acts as balancer shaft and holds the water pump. A hydraulic cam chain tensioner secures a reliable tension of the chain and therefore precise cam timing.
A few years ago KTM proved that an electric start in motocross is of great advantage. Therefore, the new 350SXF can also be started easily by the press of a button. For non-believers in the this technology the 350SXF has an option to retrofit a kickstarter to the bike.
Following starting variations are possible:
A: Only E-start (series)
B: E-start plus Kickstart
C: Only Kickstart
Engine Management System (EMS)
The newly developed engine management system by Keihin with electronic fuel injection and 42mm throttle body secures spontaneous and powerful response and maximum performance. Temperature and sea level compensation as well as the automated cold start system are state of the art. An optional map select switch (PowerParts) activates additional engine characteristics by the click of a switch. Additionally the user setting tool (PowerParts) allows the logging of data of the bike with a laptop and to change the mapping by few mouse clicks.
For balancing the rotational masses, the 350SXF engine has a balancer shaft on the right side of the engine which acts at the same time as a water pump intermediate gear and drive pinion gear for the camshaft. This solution secures a very compact overall design of the engine.
Transmission and clutch
The newly developed five-speed gearbox was designed to suit the engine characteristic of the 350SXF and shines with a very precise shifting. The hydraulic clutch by Brembo guarantees a light operation and good controllable modulation of the clutch.
The new 350SXF engine has two oil pumps similar to the 250SXF engine. A pressure pump supplies the crankshaft, piston and valve train. Additionally it supplies lubrication for the clutch and cools the ignition. A suction pump evacuates the crank housing and lubricates the gear box. This creates a vacuum in the crank housing to increase the engine performance.
The perfect combination of playful handling of a 125 and engine power close to a 250 four-stroke. In many countries the 150SX can be raced in MX2 class and becomes increasingly an alternative for all who like the easiest handling and reasonable costs.
New for 2011:
new Chassis (PDS)
improved rear silencer
air flow optimised intake boot between filter and carburettor
noticeable increase in power performance
For years KTM has committed to the development of two-stroke engines which are an advantage against four-strokes in many aspect. Unbeatable is the power-to-weight ratio, lower cost of acquisition and maintenance, and simple to service and rebuild, which allows a piston change without having studied engineering.
New for 2011:
new chassis (PDS)
air flow optimised intake boot between filter and carburettor
new exhaust (new shape, bigger diameter at connection pipe)
new two-component rear silencer (better connection, bigger inner diameter)
newly developed cylinder (lower exhaust port, new timings, optimised exhaust control)
noticeable increase in power performance
All I ever wanted was a spamburger.