Being that I can't leave well enough alone I changed my jetting again. I ordered a 128, 130, and 132 main jet for when I go with a 331 kit. Tonight I put in the 128 (replacing my 125) and removed the airbox lid entirely (I had been running the lid with no snorkel). I also went back to the stock gearing from the 13/42 I had been running.

Results:
Even being 52 degrees out the bike fired up quickly with the choke on, 10 seconds later I closed the choke and it had a nice even idle. No hesitation when rolling the throttle on either. There was a noticeable jump in power compared to what I had been running. On pavement rolling on the throttle previously the bike would pull pretty well up to around 7500 rpm and then it would start to crest power wise. Now it pulls with more authority than it did even at 13/42 (in the first 5 gears anyway, the overdrive 6th is still blah) and pulls hard to redline, no drop in power.

In the dirt the first4 gears will break the tire loose even in wet pack sand as soon as the revs get over 5K. With the airbox lid removed, it responds RIGHT NOW when you crack the throttle, I can't imagine what it would be like with a pumper and an extra 83 cc's added to the mix.

I had tried running it without the lid before and it would surge above 7000 rpm so I figured it was lean with the 125 main, the 128 seems just about right. Its probably a touch on the rich side as I'm only running the stock 300 exhaust but I didn't see an in between jet size, like a 126.5 or anything. I also have the Iridium spark plug but didn't install it yet, I didn't want to foul it if the 128 was too rich.




EMS, for another shot of juice, try a 128 or 130 with no airbox lid.

 

From my past experience with the KLX300 and 250 the 128 or 130 with no air box is usually the way to go on a 250.The way you say it responds sounds like your probably good to go. Once you get the CVK dialed in it's good for a pretty wide range of elevation change without having to mess with it. That was about the only good thing I could say about them for off road use. If you think you haveresponsiveness now,you definitely need to try a properly jetted pumper carb such as an FCR35, which is what I have. IMO it would really compliment that big bore.

 

Yea, the 128 is the way to go... my bike is runnin the best ever, i did take the snorkel out of the lid, and it seems to be runnin good all across the band... so i think im gonna leave it go.... i put 150 miles on it yesterday, its nice to have it back. Great weather, was in the 60s and sunny.... perfect

 

I'm running a 137.5 right now, hehe, summer jetting for my flat side pumper.

Put 500 miles on it yesterday, all pavement. Oh, what a literal pain in the azz! A friend of mine was going for the 'Iron Butt' awared, given to those who can ride 1000 miles in less that 24 hours. I lent him moral support for the last leg of his journey which we finished at 3:15AM. Istill don't see the point of such torture, buthe was doing it alone, so I didn't want to read about himfalling asleep and crashing. Got to test my new Belstaff and Ku****ani ridinggear, because it rained on us for aabout an hour. Came out ofit bone dry