Any advantage to removing the snorkel and covering it with a mesh screen? Or drilling holes in the airbox to increase airflow?

Air intake is only part of the picture. It greatly depends on your usage and your needs and the riding conditions.

If all you want is a cheap performance improvement then you might get 1-2hp with a modified snorkel by opening it up a bit but probably not more.

When you talk about modifying the snorkel there are two things to consider, the volumne of air and the pressure of air (whilst moving). Usually a snorkel or air intake is designed to optimise the volumne of air within a speed range (this equates to pressure). If you change the shape of the snorkel then you affect both these factors. Think of it like a driving straight into the wind with your mouth open. The more you open your mouth the great the volumne of air that enters. If you just drill holes on the side of the air intake then this will have little to no effect. However if you open the diameter of the air intake or snorkel then this will allow more air to flow into the engine.

The follow on (for all combustion engines) is the air-fuel mixture. Do you have a carby bike or is it fuel injected? If it is fuel injected then short of getting a new chip or a power commander you won't be able to modify the richness of the fuel to compensate for the additional air intake. Which means that your bike might end up running a little leaner and not giving you more power.

Again consider what you want to achieve before making mods that will change your bike.

I would also lookup other forums and experiences from people doing the same mod on your model bike before doing irreversible changes like drilling holes.

Personally I use a pre filter on my GS snorkel which has the effect of slight reduction of airflow which compensates for my K&N filter but also stops bigger particles getting into my snorkel in the first place. In theory it should prolong the maintenance times for the air filter but I still clean it more regularly than the manual states and I also clean it more often in dirty or dusty weather.

In fact this is probably the best advice. Cleaning/Replacing your air filter regularly will ensure engine performance is optimal but also prolong the life of your engine.

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TurboCharger + Francois (our BMW R1200gs) '07
www.riding2up.net, blog.riding2up.net

Ive used the search function to check all the post's and threads in the past on removing snorkels in the hope of unleashing more power but I think the general consensus was it doesnt make much difference. I used to ride 350LC's and YPVS's and everybody drills their air boxes on them but I kept mine standard and the bikes ran great and 100% reliable whilst others were always having to mess about with jets n stuff.

Our bikes are just plodders but OK ones.

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Yamaha TT600RE 2004
Yamaha YZ250 2 stroke 99

The general rule with the older Yamaha's is that standard their settings are pertty rich, so a slight increase in airflow by opening up the airbox will improve performance slightly, as the mixture improves.
Actually the most important function of the snorkels is intake noise reduction. While doing that it also increases intake pressure drop and general resistance (and the energy expended just to 'get the air through').
Om my old tenere I just removed the snorkel and it's holder plate from the airbox, which added 2 hp on the dyno, and a bit of noise.

Depending on which bike you have I'd just try it and then see how she runs. If she feels harsh and feels like a cold engine even after warming up, she's too lean, otherwise, succesful mod.
Do not worry too much about lean, that's a bit of hype thing.

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Auke
http://aukemarieke.blogspot.com

kenymact, what bike are you talking about?

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Yamaha XT600E '01, Honda XR400 '03, Yamaha XT550 '83

2002 xt 600e but am now the proud owner of an 86/7 tenere....time to mess around and see what can be done.....

I had my '03 xt600e on a dyno with snorkel of, pipercross airfilter, and opened up stock exhasut. It was still on the rich side, so no worries.