WHAT YOU SHOULD KNOW ABOUT FUEL-INJECTED 2-STROKES: MR. KNOW-IT-ALL

The KTM 250XC-W and 300XC-W TPI have been on the market long enough now to generate an established bank of information. Mr. Know It All receives a boatload of questions every month on the bike. Here are some established facts that we have gathered so far. As always Jeff Slavens is a great source of information on the bike.

Seizures: The most common seizure is a “cold seizure,” which is caused by riding too hard before the engine is up to its normal operating range of 175 to 185 degrees Fahrenheit. Cold-seizure definition: when the piston heats up/swells faster than the cylinder and the piston-to-cylinder clearance is lost.
Oil-pump failures: There is a lot of talk about the pump not providing enough oil or completely failing. This is a non-issue because I have not seen any failures, and the pump rate is more than adequate. It’s made by Mikuni, and they have been making quality pumps for many years.
Cracked fuel filters: The 2018 250 and 300 TPI models had quite a few cracked or poorly sealed fuel-tank filters. They leaked at the seam where they were glued together. The result was a loss in fuel pressure (should be 50 psi) that made them start hard and have lean/weak power. The problem is easily diagnosed with a fuel-pressure gauge or by looking in the fuel tank. If the filter is leaking, there will be air bubbles in the fuel and sometimes they spray fuel horizontally across the inside of the tank.
Is the oil pump activated by the ECU? Yes, the ECU controls the oil pump.
Is the oil pump adjustable? With the stock ECU, the pump rate is fixed. With a GET ECU, it is adjustable with the software, not the phone app.
Does the oil pump have the same pump rate for all rpm? No, it varies according to rpm—about 150:1 at idle and around 30:1 at high rpm.
Is the TPS adjustable? It is not manually adjustable or electronically adjustable with the stock ECU. With a GET ECU it can be set with the kill button and the wake-up dongle and can also be adjusted with the software.
How to prime the oil pump and why? If you remove the throttle body to install reeds or to perform other maintenance, you must remove the oil line from the throttle body. This often creates an air bubble in the line, and the bubble needs to be removed via the priming procedure. Hold the throttle wide open (may require an assistant). Plug in the wake-up dongle. Wait at least 5 seconds, then release the throttle. If there was air in the line, you will hear the pump clicking. Wait for it to stop clicking and unplug the dongle.
Does the fuel injection adjust for elevation? Yes. The fuel-injection system is called an open-loop system. That type of system does not have a Lambda sensor (like street bikes and autos) that adjusts the air/fuel ratio as you go up or down in elevation; however, it does have an ambient pressure sensor that signals the ECU to make minor program adjustments as you go up and down in elevation. This does not work as well as the Lambda, but it does help.
What does the stock Six Days map switch do? The handlebar-mounted map switch on 6 Days and Husqvarna TE models changes the ignition timing curve from the standard mode to a more mellow, dumbed-down mode for slick conditions.
What does the cold-start knob do? When the engine is cold, the FI sensors report that information to the ECU and it richens the fueling. KTM claims that you should pull the cold-start knob (which adds air) to compensate for the additional fuel. My experience is that pulling the knob makes it start harder.
Should I add a little pre-mix oil to the gas? No. Fuel is injected into the transfer ports (TPI = transfer port injection), and the fuel transfers to the top of the piston and the combustion chamber. The additional oil would never reach the piston skirts or the bearings. There have been people who have clogged the fuel filters when they run premix.
Two overheating issues: The TPI models tend to run a little hot because of the lean stock fueling map. If you own one and have some miles on it, look at the head pipe portion of the pipe. It’s likely purple or blue from extremely hot exhaust gas temps. This overheating scenario doesn’t cause the engine to boil over the coolant, but it can cause premature engine wear and poor performance.
     The second overheating scenario is caused from lack of airflow. When climbing gnarly hills in first and second gear or picking your way through a tight, rocky ravine, there just isn’t enough air flowing through the radiators to cool the engine. The only cure is a fan kit. I set my Trail Tech unit to engage at 188 degrees.

 

Jeff Slavens listens to Tom Webb’s report following a mapping change to the Get ECU.
Jeff Slavens listens to Tom Webb’s report following a mapping change to the Get ECU.

 

Comments are closed.