New owner of 2010 KLX250S
 

Well, I finally got around to buying one. It's a pretty well cared for 2010, looks great but does have 12k on it.

The first thing I need to work out is the fueling. The previous owner put on a pipe and a DJ jet kit. Bike seems to run great, but has waaaaay too much decel pop for me. I know this is sacrilege, but I don't care about the power. And the exhaust is louder than I would like anyway, basically prevents me from ever taking it to work in early AM--my neighbors would not be happy. So I'm thinking about returning it to stock. I think I have all the original parts and the remaining parts of the DJ kit, and the original muffler.

So what do you guys think? Keep the pipe on and try to fix the pop somehow (I can live with not riding in the early AM), go totally stock, or go to stock pipe and just stage 1 of kit. Keep in mind I have just basic mechanic skills, and this will be my first carb work.

EDIT: Just noticed I'm missing the intake duct (part 14073) on the airbox. I guess he was trying to flow more air...

Congrats and Welcome! What pipe does she have? Some pipes offer a quiet core insert.

Open exhaust with proper jetting will have decel crackle and popping which does NO HARM! This is not me speaking, it is Mikuni America, Dyno Jet Research, and a trained professional HD mechanic (can you say two big single cylinders?)

Read this link
Watch these videos:
Both videos back up what Mikuni says. Exhaust crackle and light popping are normal to the well tuned engine - carb or injected. They all indicate that a free flowing exhaust system and air injection pollution systems exacerbate the situation, that the mufflers on the bikes actually mask or baffle the popping, that it was there and you likely never knew it.

Chase the exhaust pop tail if you wish, but unless you are experiencing big backfires, it is normal. The really funny part to me is in researching this, it came to my attention that a lot of car people want to know how to INCREASE the exhaust crackle. Vette, tuner, and sports car people seem to like it and it is associated with performance and well tuned vehicles. Seems a lot of race tuned vehicles crackle. I remember hearing the crackle of the Ducati 916 super bikes at Mid Ohio when they came into the sweepers like the Key Hole and Carousel corners. Off the throttle they crackled and popped sweetly, some short flames out the exhaust.

As a point of reference, I'm about 400 feet above sea level, running a full FMF with Klxster's lidless formula and a 40 pilot. I have very little decel pop/crackle (not enough for me to notice most of the time)... so most likely you can reduce or eliminate most of it if it really bothers you. As KLX678 said, I don't think it hurts anything and at times, adds character.... but I get tired of exhaust noise after awhile, so I understand trying to get rid of it. I don't think DJ kit came with pilot jets so it is most likely the stock 35.... you might try a 38 (or even a 40) if you are close to sea level.

Going back to stock exhaust is like giving back some of your Halloween candy..... you could do it... but what's the fun in that?

Carb work on the KLX is not difficult.. just take your time and pay attention as you take things apart.

Junker, when you buy a used KLX with a previous owner that has "monkey'd" with the carb, you can't know what you have until you become knowledgeable about the CVK. If the PO was the original owner, perhaps he can tell you exactly what has been done to your carb. Specifically, whether or not he "drilled out stuff" inside of it..

If your airbox is lidless, and you are going to keep it that way, you will need to be running one of my lidless recipes. See my signature line for the process of gaining knowledge..

If you just want rid of the decel pops, make sure the exhaust system is not leaking, the air injection system is deactivated and the plugs for it are not leaking, install a #40 pilot jet and set the fuel screw to about 2 out..

You are going to be researching in here for many weeks, so enjoy..

P.S. Don't mind KLX678, we all know he wants peeps to be happy with decel popping...

Why yes, KLXter, yes I do want them to be happy with it if they want to be.

Why should they chase their tail thinking something is wrong? I guess you like chasing your tail, right? Why waste time on things that don't matter. If someone is bothered by it, then do whatever, but if it is the question of anything harmful they have no worries.

Don't you think the people at Mikuni American and Dyno Jet know a more than you do about the subject? I have yet to find any authority saying there is a problem with exhaust crackling and light popping. Have you?

At least you're consistent when it comes to being flippant and insulting . If it makes you feel the bigger man, go ahead and do so. I will learn to take it in stride, since it clearly is part of your nature.

It's an FMF Powercore.

oh, I know. I just find it annoying in excess. My dynojet tune on my Harley had it. I switched to an FP3 and it went away with no discernible loss to me. I do enjoy a bit, but not this much.

So when people say lidless, they mean take off the intake duct? I thought they meant taking the lid off, until I realized my duct was already missing.

Yeah, so looking at what's left of the DJ kit the guy gave me, the 128 is missing and there is what I assume is the original used one in there. There is no used pilot jet in there (and you are right, the DJ kit does not come with them), so I assume it is stock. I have no idea if he adjusted the pilot air screw, but I bet he did because there was a wood screw in the box that I bet he pulled the cover with. No telling what it is set at, though. Can this be checked without carb removal? It looked like maybe a tiny screwdriver could fit in there, but I couldn't even tell if he put the cover back for sure.