Duke 4 complete airbox delete project, success! - Page 2 - KTM Forums: KTM Motorcycle Forum
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post #11 of 235 (permalink) Old 04-10-2016, 05:51 PM
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Have you ridden it yet? How's it respond?
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post #12 of 235 (permalink) Old 04-10-2016, 07:04 PM
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I've ridden mine on the street and track and it works quite well.
Plus, I currently have the throttle mapping on the mildest setting and the throttle response is still immediate, no lag at all.

I also use the rear section of the modified air box for extra storage. Tool kit, plus a few extras, fit in a marine type storage bag, secured with small bungees.



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post #13 of 235 (permalink) Old 04-10-2016, 07:05 PM
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post #14 of 235 (permalink) Old 04-10-2016, 07:26 PM Thread Starter
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Hey DR,

I haven't ridden it yet, but will post up here when I do. I'm waiting on some other parts to get powder coated at the moment.

I expect it will ride similarly to stock because the length, diameter, and velocity stack profile have been retained, though the velocity stack mouth is slightly larger than stock.
Even at 8,000 rpms, the K&N filter I designed the kit for flows 4.5 times more air than what the motor is capable of ingesting. It is a 4" diameter by 6" height filter.

Here's how that works out:
*The motor flows 78 cubic feet per minute at 8,000 rpm (2208 liters per minute.)
*At 78 cfm (the most air the engine will ever be pulling in), the motor needs an effective filtering media area of 17 square inches (110 square cm)
*The K&N filter I designed the kit for has an effective filtering area of 75 square inches (484 square cm), roughly 4.5 times more than the engine is capable of ingesting.

The filters actually really cool. It has a molded negative bolt hole on the inside of the endcap, so a bolt can be inserted through the top of the filter to secure it. It also has their X-stream end cap, which has filter media on the end instead of just a black rubber cap, so the effective filtering media is actually more than 484.
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post #15 of 235 (permalink) Old 04-10-2016, 07:33 PM Thread Starter
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Hey Flysaab,

I really like how you kept the stock airbox in there but cut out holes to see through. That looks really good. I might have to steal that idea. It looks like the main difference between what you did and what I'm doing is that I've got the filter right up under the seat and further back to keep the velocity stack the same length.
Did you create a velocity stack trumpet end, or did you clamp the filter onto a straight pipe?
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post #16 of 235 (permalink) Old 04-10-2016, 07:59 PM
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Used a straight thin walled piece of tubing, about 2" (50mm) OD, if memory serves. I just safety wired it so it wouldn't go MIA on me.
It lasted all last season with no incidents. The K&N # is RA-0500, about $37.00 US on Amazon.
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post #17 of 235 (permalink) Old 04-11-2016, 01:09 AM
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It looks like something is missing tbh? Probably just me but seeing thru the bike like that seems odd. But as long as it works its whatever floats our boats
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post #18 of 235 (permalink) Old 04-11-2016, 01:51 AM Thread Starter
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Quote:
Originally Posted by 690arrr View Post
It looks like something is missing tbh? Probably just me but seeing thru the bike like that seems odd. But as long as it works its whatever floats our boats
Oh man, I totally disagree!
The less the better. Not a fan of fairings, belly pans, luggage, mirrors, etc. As naked and light as it can get for me. I'm also a huge fan of the old look with open pods or stacks on the end of the carbs.

Everybody likes it a little differnt. That's just my tastes. I think it'll look great, but I do think this setup would look a little better with a tubular rear subframe.
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post #19 of 235 (permalink) Old 04-11-2016, 07:56 AM
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Quote:
Originally Posted by 690arrr View Post
Probably just me but seeing thru the bike like that seems odd.
Somehow, I have always taken pleasure in seeming odd, as I've had many people tell me that over the years.
Maybe that's why I like thumpers and Triumph triples so much. Odd number of cylinders. And I owned a 5 cyl Volvo for years. Definitely a pattern there. And I'm one of the few people on earth that liked the odd looks of a Citroen DS21. Now that was one fugly car to most, but not to me.

Vive la difference!
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post #20 of 235 (permalink) Old 04-11-2016, 07:54 PM
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Quote:
Originally Posted by flysaab View Post
Somehow, I have always taken pleasure in seeming odd, as I've had many people tell me that over the years.
Maybe that's why I like thumpers and Triumph triples so much. Odd number of cylinders. And I owned a 5 cyl Volvo for years. Definitely a pattern there. And I'm one of the few people on earth that liked the odd looks of a Citroen DS21. Now that was one fugly car to most, but not to me.

Vive la difference!
Top post!

dunno 'bout the Volvo though...
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