Sweet chile.

 

I read the thread that cjbiker referred to over on ADVrider and gave the set up a go. I dropped my my jet from a 128 to a 122, bought and installed a KLX300 main jet holder (key, according to the ADV author), and went back to the stock snorkel. So far I like it. I haven't put in a lot of miles but the motor seems pretty snappy. I have a 351 kit and an uncorked KLX 300 muffler and ride above 5000 ft most of the time. I'm going on a longish tour on the wee beast in a couple weeks and I'll be hoping my fuel usage goes down a bit with the new set up. It was pretty thirsty before.

The point the author made in the ADV piece that struck me was that the air intake velocity increased with the smaller snorkel. Seems to me that the piston has to suck the same amount of air regardless of the air intake size (unless you really squeezed it down) so with a smaller opening that air's got to really be moving, maybe even compressing a bit (edit: but then it has to go through the airbox and filter, probably losing a lot of velocity). With the extra hole in the KLX 300 needle holder maybe you're getting a more complete atomization of the fuel and a more vigorous burn in the piston. Maybe. As opposed to just maximizing air and fuel volume.

 

I've questioned the air intake velocity thing since the first time reading it. The velocity through the carb venturi is what it is. If you're letting more air in to the carb, the velocity is higher. Period. I don't see how a smaller snorkel increases velocity through the carb unless the whole "hemoltz resonator" thing hold true and that the smaller snorkel actually allows more air through at certain rpms than a larger snorkel or lid off. Volume per unit time and open area...velocity will increase and decrease depending orifice size, pressure, temperature, etc. Whatever. Rambling.

 

I agree, I had the same damn things stuck in my head and frankly my brain hurts and I'm done thinking about it...

Yes the snorkel would increase velocity, but an important thing to remember here is that the conservation of mass does not necessarily hold true here... as the velocity increases via the snorkel, the density of air decreases as well due to vacuum effects. Thus you have LESS air overall entering the carb.

 

My brain is going to explode!!! I may, however, re-try using the stock snorkel (as opposed to KDX snorkel) and re-jet it again. Why? Because my 65 MPG bike has turned into a 55 MPG bike, following the last re-jet for the pipe I installed. I *may* even go back to the stock pipe again.

 

Subscribed.

I'm getting ready to re-jet my new to me KLX (complete stock), so I'll keep my eyes peeled here. I've also read that ADV thread and if I'm not mistaken with Sherpa (which I briefly considered) the Aussie KLX250's have something different with the carby.

Sorry, I'm noob as far as jetting goes and I think I'm getting a severe case of information overload.

 

hay brie, quest? i ordered a DJ stage 2. and the tech said just remove the snorkel and do not drill the slide.. when u did ur rejet did u drill the slide? just wondering what i should do, the forums here say drill it but all the bikes are 2006-2009.. any info would be helpful.. thanks in advance

 

No I did't drill the slide. Even though I read on here to do it, I stuck to the manufacturers instructions. Afterwards I felt the bike didn't start as well as before and wished I did do it. But after a few weeks of playing with the mixture screw I was able to get reliable fast starting. So in hindsight I guess I'm glad I didn't do it. If however in the future I have problems with starting and I have the carb out I'd probably do it.

Sorry I couldn't give you a more definitive answer.

 

I don’t think you two are talking about the same thing. Kayelx250S is referring to the slide. If you use the supplied spring in the DJ kit then DON’T drill the slide out. Brien I think is referring to the enriching jet, those typically get drill out if you are having problems with starting. They have nothing to do with each other.

 

thank you both for the responses! cmott i purchased the DJ (2152) as per the tech he said just remove the snorkel put the lid back on and follow the instructions of the kit..im assuming the 2009 and the 2012 are pretty much the same.. can u tell me what mods u did to ur airbox and what filter ur using, and how is ur bike running.. thanks man!