K&N Airfilters ?

Discussion in 'Technical' started by ray23, Oct 21, 2007.

  1. ray23

    ray23 Ol'Timer

    Do they really enhance performance?

    Will you have to modify the carbs when you use them Not cheap the place I saw them 3995 baht.

    I'm thinking about it for a 400 Dragstar, see if I can get a little better performance without making the engine fragile in the process.

    I know how to gte a lot more preformance make it a 1100 CC but Mai me Tung LOL
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  3. irv327

    irv327 Active Member

    The only real problem, if you replace the airbox with clamp-ons, is the lack of water-proofing.
  4. ray23

    ray23 Ol'Timer

    With the rains we have here and the fact I ride in them as they come up that could be a real problem. The bike stock is really very reliable the best I have ever had here, so maybe the real answer is to just leave it alone. I seldom ride more then 110, but it doesn't have much left after that. It's passing that bothers me, I like to get it done quickly and get back in my lane. Maybe kicking down to fourth gear will solve that.

  5. Pikey

    Pikey Ol'Timer


    If you work on the induction side of the engine, to have any real benefits you need to do the same on the exhaust side. A "stage 1" tune usually consists of less restrictive air filters (such as K&N), a less restrictive end can or muffler (usually louder too) and then you have to jet the carbs to match. As for your concerns about waterproofing, why not look and see if there is a freer flowing replacement element that will slot right into your airbox? You might find that Twin Air or Unifilter do something for your model.

    110 as a max speed seems a bit low - I'd reckon something like your bike should pull to about 140. Is it able to pull to the redline in top? If not, you could lower the gearing a tooth on the front sprocket and see if that helps (if it is chain drive of course - I am not familiar with the model).


  6. ray23

    ray23 Ol'Timer

    Ya I was thinking that one change wouldn't really do the trick, not a mechanic but it does seem if you have that much more air in you would have to rejet the carbs.

  7. mikerust

    mikerust Ol'Timer


    According to a theoretical formula I found some time ago which is reasonable accurate a 400 Dragstar putting out 32.18 Hp should be good for 154kph or 96mph. So you should be able to cruise at say 80-85% of that say 125-130. Peak power is at 7500rpm and peak torgue at 6000. If you are not turning 6000+ when you pass you are no getting full wack.
  8. ray23

    ray23 Ol'Timer

    Well I'm still not use to the bike so maybe a tack would help, but it's a full dress bike with a windshield, so more wieght and more drag. Maybe I should try kicking down to 4th.

    Haven't cruised beyond 115 yet.
  9. mikerust

    mikerust Ol'Timer

    That maybe the key. How high is your windshield? If high
    it will be like pushing a barn door.:-(

    By rough calc I figure you are at 5400 rpm when cruising at 110kph which is below the peak torgue output of the engine. So yes drop down at least one gear and wring it's neck.

    I think it is just a question of time in the seat[:)]
  10. ray23

    ray23 Ol'Timer

  11. penetrator

    penetrator Ol'Timer

    Maybe try taking the air filter out and going for a brief ride to see if it makes much difference performance wise, if it does then you know it's worth getting a less restrictive filter. Just avoid any dusty roads.
  12. monsterman

    monsterman Ol'Timer

    I have used K&Ns for tuning and replacement on many bikes , Triumphs , HDs, Buells , Ducati , Yamaha, most need some kind of rejetting and exhaust tuning to benefit, but K&Ns are reuasable and well made.
  13. ray23

    ray23 Ol'Timer

    Thanks guys really sounds like I just need to work it a bit
  14. mikerust

    mikerust Ol'Timer

    Change the spark plugs. Looking at the old ones will tell you which direction to go. If they are black then the filter may be partially plugged. Does it have one common air(box) filter or two individual. If you bought the bike used, then it is possible that the previous owner or mechanic could not get an original filter and used a piece of foam, which is now plugged up. Std. air filters are OK for everyday riding.

    There may not be a problem[8D]. It's not a 750 or 1100 so need to be revved a bit to get the most out of it. My two-stroke has nothing much below about 7500-8000 and cruises at 160 at about 9000-9500[}:)]. Strangely wearing ear plugs may improve the performance because everything sounds quieter.
  15. ray23

    ray23 Ol'Timer

    I think I just got to get rpms up. But It's not the Phantom 150 so reving it up makes me nervous I'll get used to it LOL
  16. tropicaljohno

    tropicaljohno Ol'Timer

    Also the Dragstar is shaft drive, so no chance of changing sprocket, and doesn't have a tacho, only a tank mounted speedo
  17. penetrator

    penetrator Ol'Timer

    Put a bigger back wheel on it then [:D]
  18. Klaus

    Klaus Ol'Timer

    The question is: do you really want to go much faster than 110km/h? The seating position and aerodynamics of choppers (or cruisers) is not made for going fast. On the last chopper I had I felt like my arms were getting longer by the minute going 130km/h - I felt like a sail in the wind, the helmet alomost tore my head off and every bump at that speed felt like a kick in the ass. Puttering along at around 110 seemed just fine. My CBR feels way more comfortable at 140 than the chopper at 110!
  19. ray23

    ray23 Ol'Timer

    A very accurate description, hence the large windshield, Or more accurately described the barn door LOL !! 110 is fine with me just want the reserve for passing. The way the bike is set up 130 would still be comfortabale. The 400 is a heavy bike so winds don't bother much.
  20. jonadda

    jonadda Ol'Timer

    Thier is a reason why bikes have air boxes, its to stop the carbs drawing in turbulant air, that is why they are reffered to as "still air box"
    The greater the volume of air box the better, besides C/V carbs or constant velocity carbs dont perform as well useing pod type air filters. I did know a guy in Australia though who found that he could fit 4 cans of beer in the plastic box under the seat of his dirt bike, so air boxes can have a duel purpose.
  21. salbrecht

    salbrecht Member

    Regarding K&N air filters ... DON'T.

    Please do yourself a favor and GOOGLE K&N filter tests and read about how bad they are.

    They do flow a bit more air for a while, but they also flow more fine grained dust. This is due to the low surface area of the filter. Also as a result of the lower surface area, they clog up in under 2000km or so, and then flow less air. Therefore you need to clean them quite often.

    Another very serious problem with using them on fuel injected engines is that drawing air through the oiled gauze leaves a deposit on the air mass meter, and messes up the signal to the engine management computer and screws up the fuel mixture. Step away from the K&N!
  22. monsterman

    monsterman Ol'Timer

    My personal experience after using K&N on many bikes here and in UK is that they are good ,
    All my Ducatis have the K&N filter with modified airboxes the S4 has covered over 25,000kms in Thailand with no problems and with new fuel maps and engine mods now has 119hp when i bought it it only has 101hp i clean the filter 2 times a year it only takes a few hours to wash , dry and re oil it ,my injectors and engine internals are all in perfect condition .

    but to get even more power and flexibilty i am now experimenting with aftermarket Pod filters as the airbox is a pain to remove and reinstall when working on the bikes

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