Fireteacher· Premium Member
Your explanation leads me to believe that if the airbox is removed, the carbs are going to need rejetting in order to perform similar or better than when they had the benefit of the airbox, regardless of the addition of a full exhaust system or not? Also, when the airbox is removed and the carbs are appropriately jetted, is there any difference between using two filters or four? And finally, are there any drawbacks to removing the airbox that cannot be compensated by correct jetting?FastCat said:
The deal is that the airbox is a big "reservoir" for all four carbs to share. When the engine is running, the pressure inside the airbox will be lower than atmospheric pressure, and CV carbs function based on fluctuations/differential of pressure from the head-side to the airbox/filter side. That's the short version of the explanation.
The airbox also creates a resonant pulse frequency at certain RPM's and this is also beneficial to the way that each cylinder breathes and contributes to complete cylinder-filling at certain RPM's... on a properly-designed airbox, those specific RPM's complement the way that the cams work.
not that it matters on US models anyway since Suzuki put a blank "0" jet in the bottom of the float-bowls on the US models... but the "slingshot" circuit will not function without the airbox in-place.
You could probly make a set of 36mm or 34mm CV carbs work a lot better than the 38's on a stock 750 with no airbox.
I've seen full exhaust-systems fitted to stock motors with stock carbs/jetting and the stock airbox and they still run OK like that...
but removing the airbox will require re-jetting of the carbs even with the stock exhaust and stock cams/internals in the motor.
I have seen this debated before, but I was unable to ascertain direct answers to the above questions.
Thanks in advance for your reply.
P.S. I am curious about this for my '89 1100.