usa, it may be a small displacement motor at 250cc, but it's a relatively high rpm motor. The amount of air actually moved at a given time might approach that of some lower revving, higher displacement machines. The intake opening can indeed make a difference in power if other factors like jetting and exhaust are suitably matched.

 

And also when the backfire screen is removed sporting a K&N air filter! lol

 

I am with jason on this one, no offense, BUT the directions for the dynojet kit I got I say, THIS KIT IS MADE TO BE USED WITH AIRBOX LID OFF.............pretty simple in my book. I followed the directions===I didnt question what they told me===I just did it====and guess what==I love the power I have now====Dynojet inc. has dyno'd the KLX300R with and without the jets and with and without the lid. If you want you can call dynojet and ask any question you can think of. They are more than happy to help.

 

My Dynojet Kit that I just installed today, #2182 for 2009 Kawasaki KLX250SF Stage 2 says "using the stock airbox with intake snorkel removed".

This is what prompted me to post this thread. Everyone says remove the lid, but the Dynojet instructions say with snorkel removed.

Well, I guess that I will just try it both ways and watch the plug color and see which I like better.

 

OK, I see the confusion now. The 250 kit is new, the 300R kit is what everyone use to use.

 

Think a lot of it comes down to your tolerance for noise? with earplugs I really can't ell the difference in the airbox noise, without them the open box is too noisy for me open or w snorkle removed. At that point the KDX snorkle is a happy median solution, as it kills the noise considerably.

 

The jet kit also has new Dynojet spring, says to use 128 main jet, Dynojet needle on 3rd slot, and pilot screw 3 turns out...

Guess that is the source of the confusion. Instructions for the kit are set to without snorkel removed. Guess I will try it first with snorkel removed. If it runs rich, then I will pull the lid to lean it some.

 

I have been running all year with no air box lid. I realized a much better rpm pull when I was really hammering it up towards 8-9000rpms. I say ditch the cover. With an aftermarket exhaust and my IPOD, I cant hear anything else anyways, so noise from cfm airflow was never an issue.

 

After rejetting I ran without the airbox lid but I didn't like how the airbox seemed to resonate making the intake noise quite a bit more noticable (I have reasons to keep my bike as quite as possible). I put the cover back on without the snorkel which reduced the noise level quite a bit. Seat of the pants dyno said no difference, I guess my *** just isn't calibrated to less than .1 BHP. IMHO this one is in the same pile as the crankcase breather mod.

 

Well, I got it all done today and the throttle response was SO MUCH BETTER than the stock jetting. Before it took it getting warmed up to get good throttle response (typical of lean factory jetting). Now it fired right up, idled well, with good throttle response immediatley.

I set it excatly how Dynojet said in the instructions for Stage 2... new spring, new needle with clip on third slot, 128 main jet, pilot screw 3 turns out.

Haven't got to ride it yet due to the high-temp RTV setting on the FMF PowerBomb header to Q4 muffler junction. Will take it for a spin tomorrow and then pullt the plug to see how the jetting is.