78 cb400 tii cant do 55

[sprouty]

Heeeelp!
I have just recently purchased and rebuilt a cb400 and at about 55mph are having major lagging issues. I have cleaned and rebuilt the carbs multiple times. I dont think the vacuum is off but just purchased a kit to test it. My idle wont drop below 1600 without dying. I have switched out the air box to pods but put some air filter pads inside and doesn't seem to have any problems there. I cant seem to figure it out! No issues til top end in 4th-5th.

 

[Redbird]

Bogging in the higher RPM's and not wanting to idle are signs of an air leak. Check that your manifolds aren't loose or cracked.
And, I'm not real familiar with the CB400's with pods, but my CB750 HATES not having the stock airbox on. She won't rev above 4k RPM's with the box off the bike.