Motorcycle Repair: 1977 Honda CB400F throttle bog, honda cb400f, air screws

Question
Hi Rich, I have a 1977 CB400F. At low rpm's it runs great. But once it hits around 4-5K it starts bogging down until I get back down to that sweet spot. I've cleaned the carbs and rebuilt them with Keyster kits. Now, if I close the choke about one-third of the way, it runs great all the way to redline. I've tried all different settings with the air screws from 1-1/4 turns out to 2-3/4 turns out. What could my problem be? Thanks.

Answer
The bike is still running lean.  The idle air screws only adjust the fuel mixture from idle to 1/8th throttle.  I'd recommend you check your float levels.  I think you'll find them set too low.  A couple of millimeter one way or another can make a big difference.

Regards
Rich