reading back thru this i see............
03 Blaster
Bored 40 over
34mm carb- filter on a pipe straight off the Carb
170 jet size
boysen reeds with
throttle body spacer
LRD pipe and silencer
Twist throttle
and it started running crappy after you changed crank seals.
that leads me to believe it was jetted for and while it had an airleak.
that 170 main is waaaaay to large for a stock cylinder bike, and i'm betting the pilot is also, thats why airscrew adjustments have no effect.
what pilot is in it ?
for those mods, it should be in the low/mid 40's
your airscrew will tell you
just for reference, here's my jetting for 34mm carb on a highly modified cylinder/mods
48 pilot
airscrew gives highest idle around 1.5 turns out
DGH needle (a dgh or cel needle is a must on these carbs)
155 main
your best bet is to go back to a stock 26mm mikuni carb for your mods.