K&N RK-3909-1 vs RK-3910-1 kit...HELP! - Harley Davidson Forums: Harley Davidson Motorcycle Forum
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Old 12-12-2012, 11:43 AM   #1 (permalink)
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K&N RK-3909-1 vs RK-3910-1 kit...HELP!

OK, here is my conundrum. I found a EXCELLENT buy on both of these intake kits. But the sale ends tomorrow so I have to jump now. Both use the stock air cleaner cover.

But...one uses a 9" element the other uses a 7". The 9" element is also 5/8" taller than the 7" so that will move the cover out that much.

Has anyone who has used the larger kit found it uncomfortable in that interferes with your leg position while riding?????
Bill D.
2009 FLSTC
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Old 08-12-2013, 09:31 AM   #2 (permalink)
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Old 08-13-2013, 05:13 PM   #3 (permalink)
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I had the 3909 kit and it is a fair improvement over the stock air cleaner. I have now installed the 3910 kit and it has a mildly thicker filter. I have not had any issues with knee placement or comfort. The 3909 kit will flow more than enough air for a mild build (like mine) but I had to have the thicker filter..... Good luck with either one you choose.
Remember, Ride Safe..
2008 FXSTC, V&H BSS, K&N AC kit, SE255 cams,
ThunderMax w/AT, Superbrace
Remember, Ride Safe...
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Old 08-14-2013, 12:53 PM   #4 (permalink)
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As a side note, I just put the 3909-1 kit on my FXST. Dynoed it before and after, no
difference whatsoever (it has a jet kit in it already).
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