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We are going way off topic here showing different configurations of windshield holes on race bikes that have nothing to do with the Ninja 400 and trying to link them together. The Ninja 400 has a massive gap between the body and windshield, not a few small holes in the windshield, or gaps on the top of the front fairing like the ZX10, or a very small gap like the ZX6. And while they all may have some benefit for air flow, air pressure or cross winds they are not the same design nor will they have the same effect.

Let's face some facts, if the Ninja 400 windshield gap is such a great design and has such a wonderful air flow effect why don't all motorcycles have the same design? Answer, because it is not a great design and comes with a very undesirable experience as the OP pointed out.

The ZX series and other race bikes do not share the same massive gap that will result in the same "wet dick" syndrome. Also, this gap could launch a bee or other unpleasant and now angry insect directly into my chest or under my helmet instead of deflecting off the front fairing which was my first thought. I am not sure how many of you have had a bee in your jacket or helmet but let me assure you, it sucks major ass.

Function and Design are 2 different subjects and you are tying to merge them together to make a point while ignoring the glaringly obvious poor design. Poor design is the result of incompetence or cost.

1.> Does it have a function: Yes, stabilizes air flow
2.> Does it have a good design: No, results in "wet dick" syndrome, entry point for murder hornets.

Any attempt to engineer a proper solution will require a new front fairing design or complete windshield. For street riding a simple plug should suffice.
 

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Discussion Starter · #22 ·
Just taped up the gap and went for a short ride.

Same stretch of road, four times with the tape and four times without.

For reference:
  • My bike has a + 1 sprocket up front
  • Top speed in this case is limited by the length, angle change and surface of road, hence making the run up and back twice to find a median for both in the same conditions.
Top speed

With Tape : 188 KPH
Without Tape : 196 KPH

Notes with tape:

<100 KPH - No noticeable change between the two
100-120 KPH - minor wind noise increase, as well as an increase in turbulence around the helmet up to around a 3/4 tuck. No noticeable difference to without tape in a full tuck.
120-190 KPH - Progressively worse turbulence, causing my helmet to shake around a bit - wasn't unrideable, though uncomfortable & louder. Full tuck made a minor improvement; however, turbulence was still evident around either side of the helmet.

Notes without tape:

Air flow around the helmet over 120, up to 200 KPH in a 3/4 to full tuck felt much cleaner. Turbulence was gone (at least felt like it, don't know for sure without a wind tunnel), just the usual wind pressure remained that I'm sure you're all aware of. No helmet shake, much more comfortable.


View attachment 14809
Wow great job mate! Pretty good objective test with multiple samples. Thanks heaps for the info. Had severe chest pain so couldn't get to it myself (I'm all good). Essentially you either tape/block the vent for more turbulence, less top speed but a dry crotch for the occasion rides in the rain, or you leave it as is and put up with the occasional wet crotch with the ensuing benefits listed above Tough decision hahahaha.
 

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Discussion Starter · #23 ·
We are going way off topic here showing different configurations of windshield holes on race bikes that have nothing to do with the Ninja 400 and trying to link them together. The Ninja 400 has a massive gap between the body and windshield, not a few small holes in the windshield, or gaps on the top of the front fairing like the ZX10, or a very small gap like the ZX6. And while they all may have some benefit for air flow, air pressure or cross winds they are not the same design nor will they have the same effect.

Let's face some facts, if the Ninja 400 windshield gap is such a great design and has such a wonderful air flow effect why don't all motorcycles have the same design? Answer, because it is not a great design and comes with a very undesirable experience as the OP pointed out.

The ZX series and other race bikes do not share the same massive gap that will result in the same "wet dick" syndrome.

Function and Design are 2 different subjects and you are tying to merge them together to make a point while ignoring the glaringly obvious poor design.
"Wet dick syndrome" 😂😂😂
 

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Wow great job mate! Pretty good objective test with multiple samples. Thanks heaps for the info. Had severe chest pain so couldn't get to it myself (I'm all good). Essentially you either tape/block the vent for more turbulence, less top speed but a dry crotch for the occasion rides in the rain, or you leave it as is and put up with the occasional wet crotch with the ensuing benefits listed above Tough decision hahahaha.
Or even better, drive a car (if you have access to one) when it's raining if you're worried about a wet crotch!
 

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Just taped up the gap and went for a short ride.

Same stretch of road, four times with the tape and four times without.

For reference:
  • My bike has a + 1 sprocket up front
  • Top speed in this case is limited by the length, angle change and surface of road, hence making the run up and back twice to find a median for both in the same conditions.
Top speed

With Tape : 188 KPH
Without Tape : 196 KPH

Notes with tape:

<100 KPH - No noticeable change between the two
100-120 KPH - minor wind noise increase, as well as an increase in turbulence around the helmet up to around a 3/4 tuck. No noticeable difference to without tape in a full tuck.
120-190 KPH - Progressively worse turbulence, causing my helmet to shake around a bit - wasn't unrideable, though uncomfortable & louder. Full tuck made a minor improvement; however, turbulence was still evident around either side of the helmet.

Notes without tape:

Air flow around the helmet over 120, up to 200 KPH in a 3/4 to full tuck felt much cleaner. Turbulence was gone (at least felt like it, don't know for sure without a wind tunnel), just the usual wind pressure remained that I'm sure you're all aware of. No helmet shake, much more comfortable.


View attachment 14809
Interesting findings! Well done! Well I guess now we know the reason for it. Guess you were right. It's hard to grasp what's actually going on without seeing a wind tunnel test of this or at least a CFD simulation, but your test proves that there is a noticeable difference.
 

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Just taped up the gap and went for a ride.

Same track, four times with the tape and four times without.

For reference:
  • My bike has a + 1 sprocket up front
  • Top speed in this case is limited by the length, angle change and surface of the track, hence making the run up and back twice to find a median for both in the same conditions.
Top speed

With Tape : 188 KPH
Without Tape : 196 KPH

Notes with tape:

<100 KPH - No noticeable change between the two
100-120 KPH - minor wind noise increase, as well as an increase in turbulence around the helmet up to around a 3/4 tuck. No noticeable difference to without tape in a full tuck.
120-190 KPH - Progressively worse turbulence, causing my helmet to shake around a bit - wasn't unrideable, though uncomfortable & louder. Full tuck made a minor improvement; however, turbulence was still evident around either side of the helmet.

Notes without tape:

Air flow around the helmet over 120, up to 200 KPH in a 3/4 to full tuck felt much cleaner. Turbulence was gone (at least felt like it, don't know for sure without a wind tunnel), just the usual wind pressure remained that I'm sure you're all aware of. No helmet shake, much more comfortable.


View attachment 14809
Thank you for doing this, as I suspected while reading through this thread only now - for aerodynamic reasons at speed
 
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