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Old 06-16-2008, 08:45 AM   #1
Reinhold OP
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07 640A Snorkel vs Cover

So what is the verdict? Removal of the snorkel or using a racing cover on the airbox. I’m using the cover now but I was thinking that the snorkel removal might be better for dusty conditions. Creeper was not recommending it but lots of guys have had good results. Anyone out there done a comparision?
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Old 06-16-2008, 09:02 AM   #2
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keep the snorkel
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Old 06-16-2008, 09:21 AM   #3
Seikkailu_R
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Carb dosnt know if air is coming thru racing side cover or removed snorkel.
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Old 06-16-2008, 09:24 AM   #4
Reinhold OP
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Quote:
Originally Posted by Loadedagain
keep the snorkel
Whats the reason though?
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Old 06-16-2008, 10:03 AM   #5
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Quote:
Originally Posted by Seikkailu_R
Carb dosnt know if air is coming thru racing side cover or removed snorkel.
That is not what Sommer KTM found in their tests. Supposedly the airbox is "tuned" for airflow, and while at first glance I would think the same as you, it seems the dyno didn't agree. Something about the way air enters the airbox, circulates, and enters the venturi seems to have an influence on performance...

Of course this is splitting hairs for us mere mortals - we probably wouldn't be able to tell if the same bike had the side cover or the snorkel removed (provided they open the airbox up similarly). One point for the snorkel, it might pull air across the electrics on top of the battery, cooling them, and it probably does minimize dust/dirt intake. Happe (I believe) made a screen to replace the snorkel... where is that?

Here, from the index:
http://www.advrider.com/forums/showt...=123569&page=3
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Old 06-16-2008, 10:11 AM   #6
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I threw the snorkel in the trash and have the sidecover. I might cut the whole top of the air box off too. It all helps. It all comes down to the fact that the LC4 has a airfilter for a 65 in it. WTF. I suppose that is what fits in the available space though.
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Old 06-16-2008, 10:15 AM   #7
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Quote:
Originally Posted by Reinhold
I’m using the cover now but I was thinking that the snorkel removal might be better for dusty conditions.
Trying to understand where the benefit is in dusty conditions. I think you should run with the side cover as is now and carry a spare pre-oiled filter or two when going for weekend rides in dusty areas.
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Old 06-16-2008, 11:26 AM   #8
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Are we talking air box with stock BST carb are FCR, it makes a HUGE differance.
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Old 06-16-2008, 11:54 AM   #9
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Quote:
Originally Posted by NICO
Trying to understand where the benefit is in dusty conditions. I think you should run with the side cover as is now and carry a spare pre-oiled filter or two when going for weekend rides in dusty areas.
I was just thinking that the air coming from under the seat would have less particuli () than from the side cover.
I have the stock BST
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Old 06-16-2008, 12:09 PM   #10
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With the BST I liked the snorkel removed, stock side cover. To use the race side cover with the BST, you can adjust the slide's spring to compensate for lost low end response.
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Old 06-16-2008, 12:41 PM   #11
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Quote:
Originally Posted by Reinhold
Whats the reason though?
see meats post below. best answer i can give is due to turbulence. the snorkel sends air flow rearward, then into the air cleaner. this helps remove solid dirt and debris... and from sommers tests it is also the ideal for peak torque production.
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Old 06-16-2008, 12:44 PM   #12
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Quote:
Originally Posted by Zerodog
I threw the snorkel in the trash and have the sidecover. I might cut the whole top of the air box off too. It all helps. It all comes down to the fact that the LC4 has a airfilter for a 65 in it. WTF. I suppose that is what fits in the available space though.
absolutely incorrect. while the air filter is the same as the 65 it is my understanding (with bst carb) the airbox and its vents are tuned to almost ideal. i highly recommend looking at the dyno numbers. more noise from your intake tract does not mean more power. quite often the opposite.
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Old 06-16-2008, 12:45 PM   #13
halfcab
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Quote:
Originally Posted by Reinhold
I was just thinking that the air coming from under the seat would have less particuli () than from the side cover.
I have the stock BST
I almost agree with you.
But I don't beleve the side cover flows enought air. Plus the vary fine mash screen stops a lot of free air flow. My guess is that the carb will be getting more hot air from under the seat then side cover.

Just by reading a dirty filter and having the hardparts side cover on also, my filter showed more dirt from under the seat.

"potatoho" is right about lossing some low end snap with the snorkel being removed. The loss is not as noticeable on the street.
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Old 06-16-2008, 12:47 PM   #14
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figures herr creepy was the guy who explained it way back when...

Quote:
Originally Posted by creeper
I just knew I was gona' have to jump into this clusterfuk. It's a balance of pressure... both positive and negative.

The CV works best with a slight negative pressure. Now, this is a "qualified" best in that at wide open throttle, at peak RPM, a correctly jetted for the airbox BST will make a HP or two more with an WFO airbox.
The downside is that power and throttle response at all other RPM ranges and throttle positions takes a major hit.

By balancing pressure, with the snorkel in place and the hi-flow side cover or it's equivalent installed, you get good throttle response throughout the RPM range, a nice clean torque curve without any dips or spikes and a loss of a few HP at redline.
Sommer determined, thru hours of dyno time, that the combination of the stock snorkel along with approximately 6 square inches of screened sidecover opening, under the stock outer sidecover produced the most satisfying, useable powerband... in combination with the OEM, Mikuni BST40.

An FCR, being a slide carb with an accelerator pump to compensate for the lean condition that occurs when the throttle is whacked open, doesn't really give a crap about the number of openings or their size, as long as the airbox can flow, the same as or more than, the potential flow capabilities of the carburetor itself.

Now... which is more important to you, a bike that has good useable power everywhere you use it in the real world... or a couple more HP at redline at WFO throttle?

How do I know and understand this stuff, you ask? Almost 20 years of running a motorcycle dyno has to be good for something besides black lung, blurred vision and hearing loss.

Ciao,
C
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Old 06-16-2008, 01:05 PM   #15
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Quote:
Originally Posted by halfcab
"potatoho" is right about lossing some low end snap with the snorkel being removed. The loss is not as noticeable on the street.
I was satisfied once the AFR mixture was adjusted. That was the only issue, that with a change in the intake, the BST needed to be adjusted to give the proper slide response at part throttle.

Impressively simple to adjust the BST for flow changes versus my current EFI system, in which case it is not even possible to create a proper curve for a low flow exhaust without an external Power Commander. I can choose either low/mid or mid/high but not both because there is only one fuel curve in the crippled Husky/Mikuni implementation (no active FB2/FB3 parameter).
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