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I have recurring nightmares about the airducts, filters and other debri being sucked into the motor, and I have seen a few motors where this has happened. So I went to my local plumbing supplies and bought a couple of 90mm overflow vents for a rain water tank and then modified and fitted them as per the photos. It's not proven yet as it may impact on the volumetric efficiency, but they are fuel resistant and to some extent heat resistant. I'm also going to do a set for the ST4 and maybe the 999. Like I said, not proven yet.....
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I've seen screens like that over the intakes of air filter less bikes, popular on old guzzis for example. Sometimes they invert themselves and sometimes one goes missing. No points for guessing where it went.

I have the feeling that those type of screens, depending on the mesh, actually have a surprising amount of flow resistance..

On aircraft turboshaft intakes we sometimes have wire mesh for protection if they aren't filtered, but only very coarse chicken wire style with 1/4" holes or do. Granted they do suck a lot harder, but also over a larger area. Maybe some math or Dyno testing is necessary
 

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I've seen screens like that over the intakes of air filter less bikes, popular on old guzzis for example. Sometimes they invert themselves and sometimes one goes missing. No points for guessing where it went.

I have the feeling that those type of screens, depending on the mesh, actually have a surprising amount of flow resistance..

On aircraft turboshaft intakes we sometimes have wire mesh for protection if they aren't filtered, but only very coarse chicken wire style with 1/4" holes or do. Granted they do suck a lot harder, but also over a larger area. Maybe some math or Dyno testing is necessary
So much flow resistance that Honda use them in their MotoGP engines.
 

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So much flow resistance that Honda use them in their MotoGP engines.
You can tell on the photo that this is a pretty coarse screen with large holes they are using. Similar as on the intake of the turbine above. It would certainly be beneficial to have finer filtration, but whoever designed that must have had a good reason to stick to that chicken fence.

Like I said, I've seen those fine wire mesh jobs inverted on someone's Guzzi before. Started as a dome shape and then popped in while the engine was running. That tells me that there must have been a significant pressure difference between both sides, and that which ever mesh they had used was too fine. So despite it mostly consisting of holes, it didn't flow well. How fine? Don't know.
 

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That mesh in the op is too fine and will restrict the airflow.
I use aluminium diamond mesh and it works just fine to keep out the bigger rocks.

I've tried fine mesh and gradually removed strands to get correct mixture and ended up with 6mm squares so it was a no brainer to migrate to the diamond mesh which is rigid and can't disappear down the orifice :)


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They work just fine as the open area is at least 50% more than the throat size.
 

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That mesh in the op is too fine and will restrict the airflow.
I agree, especially as it is flat rather than domed (giving greater area, therefore more open area).

My old Guzzi has considerably coarser wire mesh over the intakes;



Although, rather than in addition to the filter - on the Guzzi, it is the filter... :eek:
 

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It鈥檚 not a filter. It鈥檚 a cage to stop you鈥檙e legs from getting sucked in at full noise 馃ぃ
 

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..or low flying birds perhaps.

It seems that if the original intent is to keep detritus out of the engine, a mesh with a large enough gauge to not obstruct flow would allow sand and grit. So forget about it, run a good filter, and make sure it seals well to the airbox.
 

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Some people wear condoms, some don't.
 

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No sea too ruff......
 

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Had one picture also saved, that I found interesting.
View attachment 976010
I agree, especially as it is flat rather than domed (giving greater area, therefore more open area).

My old Guzzi has considerably coarser wire mesh over the intakes;



Although, rather than in addition to the filter - on the Guzzi, it is the filter... :eek:

Faaaaark! I think I just stripped some brain gears looking at an RC211 and a Guzzi back to back....can you warn me next time?
 

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I agree, especially as it is flat rather than domed (giving greater area, therefore more open area).
To be fair the trumpets on the OP's bike have much more of a flare on them than your Guzzi stacks, so the OD is huge compared to the throat of the throttle body. To double the surface area of a circle you only need to increase the diameter by 50%.
 
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