you have to take gas tank off.
Impossible to answer, depends on what model KTM you have.
NGK Spark Plug BR8ECM
bad plug bad plug cap stator
I have a 07 KTM 525 XCW and the manual call for 6mm on plug gap.
br10ecmix
0.60mm
NGK BR8ECM
We use the nkg br9eix
NGK BR8HS with a .032" (0.8mm) gap
0.7 mm
In the center of the head (on top of the cylinder).
NGK CR8EK or NGK CR8EiX (Iridium)