Dennis Ullrich's announcement earlier this year that he would be setting up his own team and lining up on a two-stroke machine in the ADAC MX Masters created more than a bit of a stir in the motocross scene. Ulle has never kept his love of two-stroke bikes a secret and has notched up quite a few successes on his 250cc KTM in Supercross in his time, but many experts thought his project was doomed to failure, trying to go up against state-of-the-art 450cc 4-stroke Motorcycles on fast tracks with what is considered to be an outdated engine design. It actually seemed for quite some time that the four-time Masters champion was punching beneath his weight, but he stuck to his guns and was able to show with a podium finish in Gaildorf and an equally strong performance at the Holzgerlingen finale that you can actually compete up front on a two-stroke motorcycle. He recently announced that he is switching to Husqvarna for the start of the Supercross season, so now's an ideal time to take an in-depth look at the technology behind his KTM 250 SX.
What's so special about Ullrich's motorcycle is, of course, its two-stroke engine. The best way to increase power and torque is to increase cubic capacity, so the KTM fielded by 2-Stroke Revolution Racing Team has had a 300cc factory kit from KTM Power Parts fitted. The cylinder head is from VHM. Cylinder, cylinder head and carburettor have been completely reworked. The original reed valves have been replaced with a Moto Tassinari VForce4 unit, and, as is usually the case with 2-strokes, carb jetting has to be adjusted according to the weather and height above sea level. Racing fuel from VP Racing Fuels is used, which is mixed with Motul 800 2T oil. "VP's fuel improves the engine's thermal stability by improving internal cooling," said his mechanic, Robbie Bauer. "Throttle response and the performance on tap are also noticeably better," added Ullrich, extolling the virtues of the racing fuel. The exhaust system is from HGS.
Even though you can't tell just by looking, the clutch is from Hinson. While many top riders put such demands on their clutches that the discs sometimes have to be changed in between the two races on Sunday, Ullrich is very easy on parts thanks to his technically clean style of riding. "We change the clutch discs once a year as a precaution," said mechanic Bauer. "But even that's probably not even necessary."
The suspension is actually from WP Suspension but is completely rebuilt by Mototech. "Compared to the competition, Dennis likes a fairly soft suspension with a relatively large amount of travel," said Bauer, speaking about Ullrich's preferences. He has worked with Mototech for several years now and has every confidence in the suspension specialists from the Stuttgart area.
The fork bridge is especially manufactured by FF13 for Dennis Ullrich. Its unique method of construction ensures extreme torsional stiffness, giving very precise handling. While Dennis loves this setup, it would be much too stiff for many amateur motocross riders. Like most professionals, Dennis rides with the steering top bearing set very tight, which thus also acts as a steering damper to a certain extent.
The Brembo brake calipers are made of high-tensile aluminium and are available across the counter as a factory kit as part of KTM's Power Parts programme. The discs and pads, as well as the special adapter, are from Goldfren. Ullrich uses larger discs than standard front and rear to increase stopping power. Thanks to their increased rigidity, the Brembo calipers improve thermal stability and the feel of the brakes.
The seat cover is made by Dennis' mate, Sascha Baier. He makes the 'butt' patches that are so popular in MX and also seat covers under the Germerica Deals brand name. Dennis has immortalized all his Masters titles on his bike, giving each win a star and adding the year of the win. By the way, Ullrich designed his bike stickers himself with the help of Backyard Design and took time to perfect the design. "I made several sketches and played around with many alternatives along with Philipp Klakow from Backyard Design until I was finally satisfied," said Ullrich, who has a keen eye for detail.
Titanium screws have been used throughout in order to save weight and the footrests are also made of this extremely lightweight yet very durable material. Dennis prefers footrests with sharp edges, on which his boots can find good support in all conditions.
Ullrich's bike has BRC wheels with Talon hubs and Excel A60 rims. The painted anodized spoke nipples look absolutely brilliant on the immaculately prepared KTM from 2-stroke Revolution Racing Team. The tyres are stock Bridgestones and utilise Mefo Mousse both back and front in races.