[FastCat]

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.

Additionally...

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.

 

[FastCat]

The Mikuni RS "flatslides" *are* "smoothbore" type carbs... the stock carbs are NOT what people mean when they talk about "flatslide" carbs - The OEM carbs are CV carbs, even though technically-speaking, the slides are flat.

 

[FastCat]

Donnie Darko said:
yes i know the stock ones are CV "constant velocity" BUT I didnt know that Mikuni flatsides where the same as smoothbore thanks for the info now with the flatsides would that resolve the issue with the air box?? or should I just just re jet the stock carbs ?

I'm running CV's on mine - so of course, I'm biased.

Having said that, I think you'd end up with the same mid-range/low-end problems with Mikuni RS36's as you'd have with the stock carbs and a jet-kit with no airbox. ...If you fitted some 33mm "flatslide" or "smoothbores" then that might work out better... It doesn't matter what type of carbs you fit really - you're limited by the airflow demands/characteristics of the cams/valve-sizes/piston diameter and stroke of the motor - 38mm carbs with no airbox will be a driveability/tuning-disaster on a stock 750 motor. Period.

That's my opinion FWIW.

 

[FastCat]

Donnie Darko said:
so where do I fine some of these Flatslides?
...

If I wanted some, I'd call Dwayne at Cycle Concepts:

Cycle Concepts- High Performance Specialists
1625 Lynwood Dr
Lancaster,SC 29720
803.285.8093