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KTM Duke 390: How I solved random overheating & stalling issues

31st January 2024, 15:09 by Ananth Iyer

The bike now runs cooler by one bar on the highways. Bike stays on 7/8 bars much longer before moving to 9th than before.

BHPian SunnyBoi recently shared this with other enthusiasts.

After I made a mess of installing the tank stickers, I got another set of just the tank stickers. I then took these tank stickers and remaining stickers to a good friend and distinguished BHPian, audioholic. He did up the stickers on the bike - we ended up peeling all other stickers an replacing them with new units. Here I saw another mistake, the tank stickers I've got are from a Gen 1, rest of the stickers are Gen 2! sigh.

Bike still looks good though

I was out riding today and got stuck in a big pocket of traffic jam. The temp went up to 9 bars with the fan kicking in. I then stopped at a gas station for fuel and was stationary for about 5 minutes with the engine off while waiting my turn. I filled up the tank all the way up and as the petrol stopped, one of the attendants pointed out some fluid, they assumed it was petrol, flowing from under the tank.

I kinda guessed it wasn't petrol, since I've routed the overflow pipe for it on the left side, away from the exhaust. I felt the fluid which had leaked out and it was definitely coolant. Parked the bike on the side and looked around, there was no leaks from any hose or the thermostat. The fluid level on the overflow bottle was above MAX so I'm pretty sure that's where the coolant came from. After another couple of minutes, it reduced to the max level. I started the bike and set off, I did not have any leaks afterwards.

This kept happening as I keep topping up the fluid level in overflow bottle to Max. Now, everyone would probably say head gasket (!). Now I wouldn't dismiss that as a possibility but I'd like to try something simpler and see if that was the reason. Hence I went out and bought a new Radiator cap, hoping that is the culprit - Not enough to hold pressure and prematurely ejecting coolant into the expansion tank.

I got a pair of EBC pads for the rear too, to match the EBC pads up front.

Few days later, the new rear pads went on. You can still see the factory radial flattening marks (?) on the rotor. Just shows that I don't use rear brakes at all.

Changed the radiator cap too

I forgot to drain the overflow tank before opening the radiator cap and the tank completely drained out. I replaced the coolant on the overflow tank with just distilled water since I was planning to change the entire coolant soon anyway.

Did changing the pressure cap help? YES! The bike now runs cooler by one bar on the highways. Bike stays on 7/8 bars much longer before moving to 9th than before. There was one instance when the temperature touched 10th bar when I was stuck in a very bad traffic jam. I panicked a bit and switched off the bike. I kept observing the overflow tank, and it quickly started filling above max. I quickly started the bike and let it idle, realising the radiator fan turns off when I kill the engine as well. Once the temperature reached 9 bars, the coolant overflow level was back to max level.

I've been using RON95 fuel on the bike since the beginning. On one of my recent trips, I had to fill up emergency fuel as I was close to running out. Ended up filling with standard RON91 petrol. The bike started stalling at low speeds whenever I clutch in. I had this problem before and it kinda sorted itself out when I switched to RON95. On first glance, it would seem that the stalling has now returned since I've gone back to the worse fuel, however I decided to stick with ROM91 and see if I can sort out this issue. Perhaps the clutch switch has gone bad? I went to the service center and got a new one of those.

I had just set off on one of my trips and the bike stalled just a kilometer from home. The bike just refused to start even after multiple cranks. Then suddenly the CEL light started flashing - two long blinks and five short blinks. I googled what it could be and sure enough, I got a positive result from this forum

This meant the side stand switch was preventing the start. I waited couple of minutes and then the bike started. The bike kept stalling throughout the trip though and I had decided the side stand switch had to go very soon. Recently one of the fork oil seals popped and started seeing leaks. That needed fixing as well.

Popped into the KTM service center to get the clutch switch and side stand switch. Turns out the Fork Protector LH was back in stock along with an extra belly pan clamp I had ordered couple months ago.

The D-Day for bike fixes arrived. First thing was to get the bike cleaned as it had been 2 months since the last wash

Clutch switch swapped for a new one. The old one was very rattly and loose, a part of it had broken off sometime.

Next was the side stand switch. Removing it from the bottom was straightforward with two M5 bolts. However, I could not get the old sensor out, the connector was too big to pass through the chassis. Only way to remove it intact was to disconnect the end can from the header, move it back, swap the sensor was put everything together. I've had a lot of problems with the end can because its been welded ( all my issues are detailed in previous posts ) so that was not happening.

I could just snap the old connector and slide out the wires. For the new sensor, I could route it differently. One of my friends had done this same thing, his SS wiring kept fouling with the exhaust and ended up burning the wires. The next solution was to de-pin the connector, slide it out.

Ofcourse I couldn't find my de-pinning kit. So in a pinch, I took some 1sqmm wire, bashed the end with a hammer to make it flat. It worked very well to de-pin the wires