I just did an oil change on the Duke. Very easy.
1) Remove lower cowl. 4 bolts. 4mm Allen I believe.
2) Remove drain plug on left side of engine. 18 mm socket. Behind the drain plug, there's an oil screen. Pull out with pliers. 11 lb/ft torque for the bolt.
3) Remove oil plug/oil screen combo #2 under the engine. 13 mm socket. 9 lb/ft torque.
4) Remove two 8mm bolts on oil filter cover on right side of engine. Remove filter. This is tricky as the stiction from the oil holds it in there tight and there's little to grab.I gently tapped a hole in top of filter with screwdriver then gently pried it out. 9 lb/ft torque for screws.
I bought the KTM oil change kit, part #90238015010. Pretty good deal for $20 USD. You get both filter screens, a new oil filter, new oil plug and new oil filter cover gasket. Filter screens are cleanable and reusable. This allowed me to have one set of screens clean and ready to go. I rinsed them and put them in my ultrasonic cleaner and they came out as new (bottom pic).
I used Amsoils new(ish) oil 15W50 for euro bikes in their "Metric" line of motorcycle oils. I was going to use their dirt bike oil..but decided on this one for no particular reason. The fill takes 1.7-1.8L or so of oil.
Once the oil is refilled, idle the bike for a couple of minutes. Turn off and wait 1 minute for oil to settle. Lift bike off stand and lightly tip the bike left then right. Now hold upright and look at oil fill window to check level.
I was expecting metal bits in the screen and was not disappointed! See pics. This is normal. The bike comes from the factory with a special break in mineral oil.
Pics below with comparisons new to used parts.
Next up? Valve adjustment.
