Im ready to do the carb and have a couple of questions.Why do you change the pilot jet from #35 to #40? I have the 2206 DJ kit and it is not included or even mentioned, is this necessary.
Thanks, Rick

 

Follow the kit directions. You don't change the pilot unless you have a special problem. That's why it is not in the kit. I would recommend removing and cleaning the pilot jet while you are in there. It's had 5 years time to accumulate funk.

 

You're gonna get some varied opinions about this pilot jet issue, and you have to realize that you can't usually just plug-and-play someone else's carb jetting and settings. The bikes are not all exact, the locations vary, and even some preferential issues can apply. I'll go out on a limb a bit, however, and say that IMO the 40 pilot jet is rarely a good match to a KLX250S. Some are using the big pilot jet to overcome the cold start issue with the OEM carb setup. This does help a bit, but think about what happens on a warm day and/or when you climb in altitude. You will often have overly rich jetting at idle and just off idle throttle response. Your pilot jet should provide clean operation at idle and be very clean and crisp when you crack the throttle. Too lean or too rich are both bad. Cold starting should be addressed by drilling the starter jet. Some with bigger and bigger displacement kits can probably very well go up on the pilot jet in some cases, but where that is can still vary. A 40 pilot is huge for a 250.

I installed a 300 jug on my '06 KLX250 and started with a 38 pilot jet in the carb. To my surprise, I had to go back to the OEM 35 pilot for optimum performance. Only somewhat of a surprise, because in reality you're often increasing the volumetric efficiency in the engine in some of these mods, and it's not that unusual to end up with a not too different a jetting setup. I already had a full Muzzy exhaust, all the airbox mods, and a DJ kit in the 250, and my jetting remained the same all across the board.

You're installing a DJ kit, and I think that's wise, because the stock needle just sucks. Stay with the 35 pilot jet for your 250 to start with. Unless you do some more aggressive mods, I bet that's where you need to be.

 

Any chance I could buy that 38 from you? My 35 gives me a lean pop that I can't get rid of by opening the Kouba screw as far as I dare (about 4 turns!).

 

B58, I'm not sure you'll ever completely get rid of a little decel popping. Every dual sport and off road single I ever owned that had an aftermarket pipe, DJ jetting, and airbox mods did this...XR250's, KLR600's, KLR650's, and this KLX250...oh, and even an old antique, air-cooled, '79 KLX250. It's probably a debateable issue, but I think that slight pop on decel is the sign of spot-on, low end jetting. Now granted, if you have a case of popping that sounds like the opening day of duck season, you may have an issue. On the jet, I guess I'd better keep it. I try to keep a full range for any possible future use. Sorry.

 

Yank:
+1 on the above.
I installed a #38 pilot during this winter's uncorking job of a gently-used all-stock '06 purchased in Sept '10 . HMF muffler, removed airbox lid (now lid back on with a snorkelectomy), aftermarket airfilter, DynoJet 2206 jet kit with needle at middle clip position, drill slider, drill enrichment (choke) to 0.018". So, with the uncorking and carb work, besides replacing the #35 pilot with a #38 (mentioned above), upped the main jet from stock to #128. The bike started real nice, but I could tell it ran rich all the way through the throttle. It had a little bog at low throttle, more at WOT (had a difficult time hitting the rev-limiter), and black exhaust soot building in the muffler exit and on the rear fender. So last weekend, I put the stock #35 pilot back in and replaced the DJ #128 main with the DJ #124 main. No change in the needle (still DJ #2206 in middle clip position). Also have a kouba (T-handle) fuel adjustment screw 2 1/2 turns out. It's now much better than stock, and also better that the first carb work that made it too rich. I don't think it's yet dialed in perfectly, but it is better than anything else yet. Elevation may matter - I'm at 2,500 ft and ride up from here.

 

With the stock 250 cylinder, I ran the stock pilot jet at 3 turns out. It was perfect. Once I went to the 351 and blocked off the air injection (smog) and put a cap on the vacuum port of the carb, I had to go to 2.5 turns out because it was too rich at 3.

To each his own, Tune to your own preference.

Pop on decel to me has NOTHING to do with how the bike runs Its just a result of the exhaust system.

Just a note, with the 351 and Tm36-68 carb, I ordered a 15 tooth front sprocket because its got too much grunt and I am looking for 7th gear at times. This thing really has some *****!

David

 

I'm at 1000 ft. and run the 35 pilot, 128 main, clip in the middle, screw out 3 turns. Snorkle pulled, powercore4 and a powerbomb. I have no popping on decel at all, I do think my bike is just a shade rich but it runs perfect. I can pull the airboxlid and get just a bit more top end out of it and it still runs well. I am too close to mess with it anymore and it was too easy as this is what dynojet suggested and it worked on mine.

 

Thanks for the advice, and no problem on you keeping what you have. Since it only happens on decel (and I can stop the pop with very slight opening of the throttle), I doubt it's getting hot enough to hurt anything.

 

Thanks for all of the information. Got another question. Im at 250-500ft elevation, Im planing on going with the 128 main and 3rd clip. Also drilling the slide, and drilling the choke to .018. I have the FMF Q4 without the power bomb. Kouba screw out 2.5 turns. Does this sound about right?
Thanks, Rick