The KTM 250cc engine is known to be the most powerful and most competitive 2-stroke engine of the class. And things get even better. For MY18 the KTM 250 EXC (EU model only) is fitted with newly developed TPI (transfer port injection) fuel injection system, a unique feature when it comes to sporty 2-stroke race bikes. The patented EFI system with two injectors mounted on the transfer ports of the cylinder makes the engine much smoother to ride and reduces the fuel consumption drastically, a global game changer in terms of technology. On top of that, the KTM 250cc powerhouse features a modern shaft arrangement that’s beneficial in terms of mass centralization, a well-protected E-starter, a balancer shaft for low engine vibrations, a 6-speed Enduro transmission and a hydraulically operated DDS clutch. This is a song of belly tingling 2-stroke symphony when keeping it pinned on the pipe, while still being able to deliver ultra-smooth and reliable drive when you need it.
The KTM 250 EXC TPI cylinder has a bore of 66.4mm and is fitted with the sophisticated power valve providing smooth and controllable power characteristics. For the EFI application the new cylinder features two lateral domes, which hold the fuel injectors supplying fuel into the rear transfer ports. Thus the loss of unburnt fuel is reduced for less emissions, a more efficient combustion and reduced fuel consumption. A little tube in the back of the cylinder is connected with an intake pressure sensor, which supplies pressure data to the control unit. Furthermore, it’s possible to change the bike’s mood in seconds thanks to two supplied power valve springs. Limitless settings for different tracks and preferences are up for grabs.
Pre-mixing 2-stroke fuel is a thing of the past for KTM EXC TPI owners. An electronic oil pump feeds oil from the oil tank via the throttle body into the engine intake, and ensures a perfect fuel-oil mix in all conditions and engine speeds. The system, which reduces up to 50% of the smoke from the exhaust system over previous models, is managed by the control unit based on the engine’s revs and load measured by the TPS (throttle position sensor). The oil capacity of approximately 0.7 liters is enough for 5-6 refills of fuel, giving you more time to ride, less time measuring things out.
For optimal mass centralization the lightweight die-cast crankcases hold the clutch shaft and the crankshaft in a high position close to the center of gravity. Which is nice if you care about sweet handling. In addition, it allows the implementation of a balancer shaft. So your ride will be as relaxed as it is rapid. Plus, your new favorite engine will keep looking as fresh as the day you bought it: the engine covers feature a smart surface structure that reduce the wear caused by the rider’s boots.
This 6-speed Enduro transmission features an Enduro-specific wide-ratio specification and provides precise and easy shifting. Keeping safety in mind, an advanced ´No Dirt´ gear shift lever design prevents muck from blocking the joint. Because even dirt lovers hate mud when it’s in the wrong places.
Say goodbye to numb feet and hands. This engine design allows the implementation of a lateral balancer shaft in order to keep the vibrations to a minimum. You know what that means: more comfort, less fatigue, bigger smiles.
The KTM 250 EXC TPI employs the KTM-developed DDS clutch (damped diaphragm steel) with a wear-free steel basket, extremely heat resistant clutch plates and new, nitrated steel liners. This clever design employs a diaphragm spring instead of the usual coil springs, making for considerably easier clutch action. A diaphragm spring also leaves sufficient space for a damping system to be integrated into the clutch hub. The goal is traction, but durability is as well. Light operation and telepathic amounts of control are standard with this hydraulic Brembo actuated clutch.
The TPI engine is fitted with a newly developed throttle body made by Dell`Orto. It features a diameter of 39mm. The airflow is regulated by a butterfly connected with a twin-cable throttle cam, which is operated by a new handlebar throttle assembly. A throttle position sensor provides airflow data to the control unit, while a bypass screw allows the regulation of the idle speed. The cold start device also opens a bypass supplying more air. Via an oil intake tube oil supplied from the oil pump is mixed with the incoming air to lubricate crankshaft bearings and cylinder/piston etc.
This nickel-plated pipe is produced by WP Performance Systems. It is taken over from the carburetor model and designed for an optimal power band and maximal performance of the engine. A modern 3D production process guarantees top precision and reliability of the pipe, so this screamer is as tough as it is strong.
Engine management system
The engine management system (EMS) of the TPI models features a new control unit located below the seat. The control unit determines the ignition timing and the amount of fuel to inject is based on several sensor readings such as intake and ambient air pressure, throttle position, oil and water temperature. Thanks to altitude and temperature compensation the rider does not need to worry about fiddling around with the jetting anymore.
The TPI models are fitted with a stronger generator delivering 196 W (the same as their EXC 4-stroke brothers) to meet the needs of the engine management system in terms of energy supply. The new regulator is taken over from the EXC-F models.