k&n filter and jet kit

[93katana]

i recently installed a factory stage one jet kit, on my 98 katana 600 with a full d&d exhaust and now i bought a k&n filter and it runs like crap with the filter in, cruising it runs find but when you give it gas it spits,popsand cut back so now i got the factory filter back in now and the bike is running perfect can someone please tell me something to do so i want just be throwing 60 bucks away on this filter

[duff daddy]

ah, the k*n was prob putting tooooo much air in to it so when youd open up the throttle, it would pour the gas in and wayyyy tooo much air, so with how you have it tuned right now im sure its running fine, just sell the filter on here im sure someone would want it

[lucky6man]

if you changed the jets you could run the k&n. but thats more work then its worth. thats why they say do the k&n at the same time you do the jet kit.

[The CyberPoet]

Duffy and Lucky pretty much hit on the nose.

The K&N permits higher airflow rates (less restriction through the filter -- which also doesn't filter as well as a result IMHO). That in turn causes the fuel-air mixture rates to also change.

If you think of fuel-air as a combination product, it will ignite from about 8:1 (eight parts air to one part atomized fuel) to about 20:1, with about 14.7:1 being ideal with pure "ideal" 88 octane gasoline (i.e. - 88% octane, 12% heptane) -- the actual ideal changes based on the fuel content.

When you put in the K&N filter, you changed the air part of the equation, letting more air through (and lowering the vacuum back-pressure, which also decreased the amount of fuel being drawn in). This took the bike from somewhere around 15:1 ratio that the bike comes from the factory at, to somewhere much further out (I'd guess something like 18:1 at some RPM ranges), giving it crappy behavior. The two choices at that point are to correct the fueling by changing the carbs' jetting to compensate (to take it back to that "ideal" value or really close), or to return to the stock filter (with the already correct values as a result).

To tweak the carbs to set them ideally takes either a dyno machine (to add a load to the engine while testing) and an exhaust gas analyzer (to see where the exhaust is lean and where it's rich, etc), or a whole lot of trial-and-error over weeks & months (plus several sets of replacement spark plugs -- half dozen sets isn't uncommon) while you keep tweaking at it and rechecking the plugs after a few hundred/thousand miles to see where the mix is. There are other, lesser known methods (such as a special set of plugs that let you see through their base to see the color of the ignition result), but these are still not nearly as accurate as using an exhaust analyzer by far. Finding someone else with exactly the same equipment set-up who already has theirs configured correctly can save you a lot of hassle, since it should put you in the right ballpark as far the settings go (DynoJet can often provide these for certain combinations of equipment, but only if they have already tested them in-house or at one of their factory-owned garages).

Hope that clears it all up for you.

Cheers
=-= The CyberPoet

[93katana]

thanks guys that helped me out alot so i think ill just sell the filter, once again thanks for the advice

[Special K]

WAIT!

No need to sell the filter...........................

To things to check:

WHAT jets are you running?
(HINT: they ARE different if you are running a stock filter vs. a K&N)

Did you synchronize yrou carbs once you were done?
(Hint: You have to or they will not be right!)

Where you at in VA?

K

[93katana]

ok i have the factory jet kit which came with 2 each of these 112.5,115, 117.5, 120 and 122.5 jets i put the 122.5 on the outside of the carbs and the 120 in the middle and set the needle clip on the 3 i think line on the needle and its running fine with the stock filter i hope thats what you was asking me, and im on the NC-VA line