Where is main fuse on 01 Intruder VL1500K1 located. ?

Hi,normaly behind side cuver or under the seat on most motor bikes.

It is part of the starter solinoid. Unplug it and you will see the main fuse.

Ok, there are two places on this bike where you will find fuses. There is a main fuse (30amp) on the starter relay located behind the left upper cover (false fuel tank), and then the main fuse panel is located behind the right rearward engine cover. This cover has only two screws holding it on and they should be hex fittings.
DO NOT try to remove the forward cover (the one with the oil sight glass in it). That is the clutch cover/right side engine cover and is sealed. This cover is held on by regular bolt head bolts.
While your in the fuse box you may want to take note that the oil fill plug is under that first cover as well.

I don't know where the fuse box is on this model, usually under the seat. Pass button puts headlight on main beam

If you remove the green cover from the fuse box under the seat, you'll find two 30 amp fuses in there. I don't know which one is the "main". Perhaps they function together in concert, so if one is bad, both are bad. . . I derived this info from youtube, and the video was for a different model, but it was a Suzuki. They are probably similar in wiring. But, full disclosure - I am not a motorcycle guy. Good luck.