RCVTR

Ok, so let me ask you this. I don't know the answer, but it would be a good one to know in ths case.

A stock airbox is designed with a snorkel, so that the only inlet to the airbox is between the cylinders, in a calm area of air. This region is supplied with cool, ambient air through the inlet ducts in the front of the fairing. You also get a side benefit of part of this ducted air flowing over your knees and displacing the hot radiator air outward, to keep you cool. But for the engine, there is a constant, mildly pressurized source of air for the intake to the airbox. The main goal is to minimize pressure fluctuations in the supply air and maximize the supply pressure. There may be other design issues, like cutting intake noise. It is not designed t be a ram-air system, per se.

So now, you cut off the top of the airbox. The supply air now depends on the air pressure on the underside of the gas tank, which is open to the sides to the outside world, which is whizzing by at 100 MPH. We know from our high-school physics class, where they describe how an airplane wing works, that high velocity creates low pressure.

So my question is this:

Is the air pressure under the gas tank higher than the air pressure between the cylinders?

If you want better airflow to your engine, it better be.

lazn

RCVTR: you do have a good point there, he should seal off the sides and back of the interface between the tank and the airbox if he wants to improve airflow at speed.

Otherwise the low pressure created by forward velocity will try to suck air out of his carbs.

Or he could build a Ram Air duct like the Moriwaki bikes had:
https://www.superhawkforum.com/forum...ad.php?t=21875

VTRsurfer

That's exactly how a carburetor works...it's called "venturi principle". Air flow speeds up as it passes through the venturi, a narrowed area in the throat of the carb. This creates a lower pressure at the main nozzles. Higher atmospheric pressure coming in through the carb vent pushes the fuel out of the float bowl through the main jets and out the main nozzles, which dump fuel into the venturi section of the carb throat.

Plus I'd think you'd create a ton of turbulence by cutting off the top of the air box.

thetophatflash

A step in the right direction might be to install a Flo Commander to at least have a common air supply to the pilot jets.

RK1

http://www.ablett.jp/bikes/vtr/air_box_lid.htm

http://www.ablett.jp/bikes/vtr/air_box2.htm

http://www.ablett.jp/bikes/vtr/air_box3.htm

Best of luck, but I've never heard or read of this working well.

Tweety

I have spent a couple of hours trying to get that to work... Both on a stock engine and now on my modified engine... Simple answer... It makes more power, more torque and nicer curves with easier setup with an unmodified air box than anything else... I have had limited success with some mods to improve airflow in the snorkle (not remove it) but that's about it...

And I think I have said this before... I have unlimited access to a dyno... So when I say spent hours, well... You get the picture...

skoshere