NGK # system runs backwards.....b9 is cooler heat range, b7 is hotter.
NGK Sparkplug Codes
but i too suggest moving back to the stock b8es
ok, here goes. the main jet is easy, so lets start at the bottom as i feel your troubles are there.
you did get the float height correct ?
is the airscrew responding to turns ?
if not responding, jump 2 sizes both directions and try again.
find a pilot the airscrew creates response too.
if high idle is under 1/2 turn, jump 1 size richer pilot.
if above 2 turns out, try a 1 size leaner pilot.
once high idle is acheived under 2 turns out, time for mids....
what needle is in that thing ? should be "dgh" or "cel"
start with clip in middle, hows it feel at 1/2-/3/4 throttle ?
lower the clip to richen the needle until it falls on it's face/bogs, then back up one clip, then small 1/8th turns on the airscrew till it revs clean past 1/2 throttle and pulls hard when ridden.
get that far and a main jet will be easy with feel, sound and plug chops.