Motorcycle Repair: cbx carbs, service booklets, keihin carbs

Question
can u help  i have a pristine 80 cbx   the bike runs like crap till 3500 or so then runs great after.  ive had carbs off  cleaned them   .thought pilot was dirty  .runs exactly the same . all stock  .orginal airbox  has a dg 6 into one  if u hit the choke  a little  takes the fuel no prob. seams lean  backfires down low. but runs perfect after 3500 or 4000. could u please help me . thank u very much

Answer
You have blocked idle jets.  The idle circuit on the CBX Keihin carbs is tough to clean, the jets are pressed in and need carefully tapping before you can pull them out.  You can get this done by ICOA club members; the job will cost around $800.  Or you can do this yourself, in the last CBXpress there is an advert from CBX service booklets by Mike Nixon.  Buy the one for carburettors and you can do the job yourself.  Good luck,  Jan