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Discussion Starter · #1 ·
how do you remove the stock air box, I have removed the pins that hold the air box to the carbs and all bolts (i think) it wiggles around but how do you get it out does it break down into two pieces because there is no room to get it out it seems unless it breaks down HELP!!
 

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Donnie Darko said:
so just break the SOB and get new filters that dont require the air box then?
That's my plan in the near future. It makes cleaning the carbs a lot easier, looks cool, sounds cool and gives a few more horses.
 

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Discussion Starter · #7 ·
ok Well the air box is gone I had to cut it because even though I took the carbs off it still would not come out because this little nipple piece at the bottom was getting hung up so yeah I cut it !!!!
at any rate why would it make carb tuning a nightmare? would mine be a "short" stroke motor? '89 GSXR 750
 

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Yup. '89 is the other short stroke motor, yup higher ride height too. The airbox really made a difference to the tuning for me. Like being able to get the fueling right and not. See one of my earlier posts. Hopefully you'll have better luck! Troy341
 

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Discussion Starter · #10 ·
Well what about K&N replacements ? they going to make it run totally different as far as fuel mixture, I know on some carbed cycles that you have to keep the float bowls at the same pressure as the "static" air in the air box but the carbs had breather tubes that were vented to the air box and did not have a drain to prevent flooding. BUT on my bike it didnt have any kind of "breather" tube and that would be the only issue that I could see having without the stock air box. Is there something else I should be aware of?
 

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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.
 

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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.

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.
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?

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.
 

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Everything Fastcat said is correct, more so on the 750's.Unless your going to run flatslides leave the airbox on. By the way, to remove the airbox on any oil cooled GSXR all you have to do after the carbs are off is remove the alternator.
 

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Discussion Starter · #18 ·
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 ?
 

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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.
 
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