Topic: cb400f intake/exhaust

[omcginnis]

I just bought a 76 cb400f and the previous owner modified the intake with some K&N filters... he mentioned that given this modification the bike's exhaust would need modification also in order to get it running optimally.  Anyhow, I've noticed that the bike (somewhat consistently) loses almost all power between 4,000 - 5,200 rpms and then kicks back in pretty hard whenever I punch the throttle.  I've been told that it's probably a result of too much air being sucked in and my exhaust not being able to spit it out fast enough... does this sound reasonable?  Any thoughts?  What might I look to do to the exhaust to even things out?

Thanks very much.

[tom8Toe]

Does it currently have stock exhaust or has that been modified as well? It may just be a matter of rejetting the carbs.

[omcginnis]

Does it currently have stock exhaust or has that been modified as well? It may just be a matter of rejetting the carbs.

It's a stock exhaust... no mods done to it!

[tom8Toe]

Your choices I assume would either be switch out the filters for the original airbox, or rejet the carbs to larger jets. My 400/4 has "pod" filters with stock exhaust and the carbs were rejetted to acheive the nessesary response.

[omcginnis]

My 400/4 has "pod" filters with stock exhaust and the carbs were rejetted to acheive the nessesary response.

How many sizes bigger did you go on the pilot jets?