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Why remove/cut out or run with out the air box duct ??
Are there dyno tests to prove increased torque or HP
with these removed ??
I just ran today without the cover at all and the bike sounds
good but noticed nothing in power or speed.
I decided to check square inches(area) and here are my findings.
I put the carb bore and the bore of the air box duct and duct removed
on Auto Cad and found the following:

36 mm carb bore =1.58 square inches
OE top with duct installed =2.44 square inches
OE top with duct removed =4.06 square inches
I can't see where there is any bottle neck in the
air box not to mention the increased risk of pumping water
through the air filter.

There's more to it than just the cross sectional area through which air can flow . . .

Theoretical stuff:
First: Total restriction to air flow is sum of all restrictions that are in series (gets complicated when the restrictions are in parallel but that's not the issue here). In your bike, the resistance to flow on the intake is a combination of the airbox opening, the filter (and how much oil is in it), the intake boot, the carb, the reed valve, and the intake porting (and I'm probably missing some stuff). Sure, if one spot is significantly more restrictive than others, changing the much less restrictive part doesn't have a whole lot of effect, but . . .

Second: Restriction to air flow is caused by turbulence, and turbulence generated is as much a function of flow path as cross-sectional area (and very often more) . . .

The carb path, while smaller, is a relatively straight path. Now look at your snorkel! To put it in perspective, if you were to measure the pressure drop (the way restriction is measured) along various points in the water pipes in your home, you would find that the 90-degree bends have MUCH larger pressure drop than the straight sections - 15 to 20 times more! Yeah, we're talking water vs. air but the principles are quite similar.

Bottom line: opening up the airbox has a significant impact on air flow in your bike from a "physical phenomena" standpoint. Additionally because it changes the carb's pressure differential, fuel being fed through the jets changes (venturi effect). All of which should impact performance to one degree or another.

Seat-of-the-pants: I'm not sure why you're not feeling a difference (FWIW I did when I drilled holes in the lid). Jetting perhaps? Other's may have additional/better ideas on why.

Wow! And you a fellow Kentuckian? You make us proud!

I think he copied that from somwheres....

Guys,

I never thought I'd say this, but I went back to a ventilated airbox lid after running RB's carb mods without the lid for 6 months.

I am very happy with the lid back on!! The bike pulls better from low rpm's than without the lid.

I drilled 8 5/16" holes and removed the snorkel. 40/152 CEK-3 Boyesen 607's.

I have an 05 200 with a Pro Circuit platinum II, stock silencer.

ok set it straight removing the air box lid is like any other mod to the engine intake, exhaust or carb. YOU MUST RETUNE OR JET THE BIKE TO BEST PERFORMANCE WITH SAID MOD. if you read a post that some friend of a guy on the other forum slapped a xxx on his bike and it was twice as fast then its gospel?
some of the performance mods are enhanced by better air flow, how ever the bike in stock form was engineered to run with the air box lid on. engineering is a good guide line but testing by seat of the pants is always the final adjustment. just ask RET GEN Chuck Yager.

DONT FORGET THE SEAT SITS A TOP THE AIR BOX.

I agree.... a modified lid is the best way to go. Just getting rid of it is a quick test to see if the bike will respond to better flow.

At first it seems great, sounds really cool, but the honking eventually wore on me...

So I put my lid back on, but added a lil mod too it first




On my DR650, after putting a jet kit in it, it would not run right without modding the airbox. I put something like 12 filter vents in it and it would still stall on the freeway at WOT, eventually had to pop all the vents out to get it to run right

I agree, I pulled the snorkel and jetted it, I felt a good low-mid range gain.

Tougher to jet with the whole lid off though. Always had a hesitation.

Do those little filters plug easily?. Need cleaning or reverse blowing?

I can't help but think a second snorkle would be a help, while keeping the muck out.

Anybody try this?
Greg

No room for a second snorkel.

GS wrote:Do those little filters plug easily?. Need cleaning or reverse blowing?

I can't help but think a second snorkle would be a help, while keeping the muck out.

Anybody try this?
Greg

Uni Filter Vents have a foam flter, clean and oil them just like your regular filter

I've seen them pretty dirty but never plugged totally up

This has been covered very well already..but I want to chime in anyway.

Re: Why remove/cut out or run with out the air box duct ??@
Are there dyno tests to prove increased torque or HP
with these removed ??#
I just ran today without the cover at all and the bike sounds
good but noticed nothing in power or speed. $


@ Because the bike runs better with it modified.

# Not that I am aware of..and if there were I wouldn't pay any other than passing interest in them. Why? Because of @.

$ Rejetting is required.


Mostly I want to chime in on this part: It's pressure that makes the carb work. Pressure change, drop, loss...whatever. You can SEE holes in things, but you CAN'T see what is happening to air when it goes through that hole..turbulence or pressure-wise.

EXcellent example.. pipe elbows compared to straight pipe. I worked for an HVAC outfit for a few years. Where there were elbows, transitions, plenums and such had a lot to do with pipe size, length and air handler requirements.

Second...the rarified part (turbulence...or lack of it). That's one reason the RB carb works. Yeah...there is LESS volume (by cross-section) with the divider taking up space...but having it there 'smooths' the air out..and that benefit is larger than is the detriment from reduction in available volume.

I once read a write-up on 1-dir (wonder) reed cages..by 1-dir. They said that ANYTHING in the way of air was bad..and all their counterparts' work with foils, dams, dividers...ANY flow modulator was complete crap.

...and that is when I knew that 1-dir was complete crap.

Excellent info, Jeb! Heck..you know it's all right cuz it SOUNDS so good!!

(well, and it is, too)