Welcome alexiS4,

To the forum.
Not familiar with the later models but I think it's the same fiddly exercise.
The OE tool set pipe socket, needs to be fiddled on top of the cam cover, pushed up, rear end first, before it can be lowered down into the spark plug hole.
Getting the spark plug out of the hole is a complete different and nerve wracking charade but doable.

Good luck 🙏

 

Spark plug has always been an PITA for the Duke series, but with little getting used to, and a small hand helps. Your tool kit will have a spark plug spanner and as the OP said, it's a circus to behold. Good luck, you'll get there.

Cheers!

 

Mind sharing me the progress ? And what is the size for the spark plug ? Is it the same ?

 

Hello, did you replace the spark plug already? I'm looking for some information, this bike has a lot of thinks to remove before reaching the spark plug

 

You can purchase the entire Workshop Service/Repair Manual, for approx 22.50 USD, here:

https://www.etsy.com/no-en/listing/1700108004/ktm-2024-390-duke-service-workshop?ga_order=most_relevant&ga_search_type=all&ga_view_type=gallery&ga_search_query=KTM+2024+-+390+Duke+-+Service+Workshop+Repair+Manual&ref=sr_gallery-1-1&pro=1&dd=1&content_source=7b31999e4e22104e5292a24bc95aa8547290fd01%253A1700108004&search_preloaded_img=1&organic_search_click=1

After payment, you are able to download as a PDF.

 

Literally just changed my plug last night.... Took less than 3 minutes with the proper combination of tools...

1. 14mm magnetic plug socket with swivel head/extension (magnet holds the plug to get out of the head fairly easy) Link: Amazon.com

2. 13mm to 3/8" square adapter (this is the magic piece to the puzzle!!!) Link: Amazon.com

3. 1.5" extension

4. 13mm ratcheting gear wrench

I had to drop the socket in the head 1st, then with the wrench, adapter, and extension all connected, I was able to go in from the brake side of the bike and connect to the socket & remove the plug. Once its loose, I reached in and pressed the button on the wrench adapter which released the extension & removed the rest by hand... A bit fiddly, but much easier than trying to get a normal ratchet in there & only get 1.2 clicks at a time of turning on the really long plug... Good luck!!!

Note: This was on a 1st gen, but the others should be similar...