carburator air box removal modifications

[55cid]

fellas I have a friend that has a 81 honda CB 750 custom that would like a little more performance but must keep the bike quiet so he can leave the house early morn with out wakeing his baby and wife so. I will be removing the stock air box for individual filters and leaving the mufflers alone. Would like to know any of you have done this and what jet sizes thay are running and if cutting a spring loop out of the vacume diafram for the needle slide works well or not?  any help with the jet sizes and spring rates would be a great help thanks!  

[woodsrider250-2]

With the Constant Velocity carbs on these bikes (The DOHC 79-82) need the airbox to create vacuum for the slides to fully open.  Most cases removing the airbox will decrease power....Regardless of jetting.  Pull your air filter cover and filter and go for a quick ride once.   There are needles/etc that help, and are only available in the K&N stage III jet kit which is very expensive.  Different carbs entirely (direct lift type) with pod filters are a different story.  They may or may not increase dyno HP, but will increase throttle response A LOT.  Cams/bore/etc would be your best bet, but these aren't the best bikes to mod.  Just ride....

Oh yeah, ignition is a weak point (coils), a coil upgrade is a good thing.

[cbRider]

Do yourself a favor, search this forum for:Air Box
This subject comes up almost on a daily basis.

Karl

[dylansdad022102]

one thing noone mentioned. DO NOT cut a loop out of the spring in your needle slide. you will definatly regret that, they are weighted and the spring is there to bring the  slide back down when the throttle is closed and will run high rpm's when you close the throttle