valve adjustment would be as follows:
set engine to tdc.
remove the rocker inspection covers (like you did in the pic)
loosen locknuts
screw in adjusters till 'just' finger tight
move the nut into position so a corner of it aligns with the straight slot of the adjuster, hold nut perfectly still, back adjuster out till straight edge hits the next corner
tighten lock nut and do not let the center adjuster move
roll the engine twice over and recheck it before you put your caps back on.
its call the 1/6 turn valve adjustment method and is standard on husabergs and more trustworthy than using a feeler guage. do it like this.
also lateral (side to side) movment of the rocker arms is adjustable. if should be a just noticable amount i forget the actual spec, like .002-.003 or something
to adjust this you have to loosen the rocker cover hold down screws above the black cam caps on the flywheel side of engine and also one in the middle by them i think, then take a socket and tap the black cam caps into the engine as needed, or back out with a small angled bar or something till in spec.
retighten the bolts to 10nm of torque (not much)
also get used to changin that oil bud! filter every other time and i think yours is like a 5 hour interval or something then filter at 10 hours. our engine are a little different but a lot the same, i use rotella-t 15-40 (as do many berg owners so its cheaper to change than 'bike' oil) its JASO approved now for wet clutches and make them frequent oil changes hurt less......and yea you better do them and check it before every ride too....
also if your not a member of husaberg.org yet you should be......
can you see the decomp with the rocker arms off? is it manual or auto decompressor, i only have experience with the auto-decompressor so i can try to help you fix it if needed if you have the auto...
oh yea i forgot i was supposed to say congrats on the new bike too lol sorry i got carried away......just wanted to make sure a new berg guy knows a starting point at least........really love your bergs body style, if it was cheap and easy to buy a complete tank and plastic kit, mine would look just like yours when you get your black plastics...(except be way faster of course) LOLOL just kidding, 501's are pretty sweet bikes man bet it looks awsome when done.......bet it would spank your old ktm125.......