What the title says...

My pipe finally came and I got it installed Friday. Sounds incredible - nice bark to it, and not too loud. However, it pops a lot whenever I decelerate now.

I've done mods one-at-a-time so I can troubleshoot any issues more easily. Up until now, I've had the KDX200 snorkel and DynoJet kit installed, and it's been running great. I added the pipe, and the popping started. I had zero pop before putting the pipe on.

I did read just about every thread on here regarding popping... most of which were at least a couple years old. I never got a good feel for the cause of the popping (some said it was normal, some said look for leaks, and others said re-jet), whether it may be bad for the engine, or how to fix it.

I don't want to re-open a can of worms, but I'd like to make sure I'm not going to damage my engine. Any thoughts on the decel popping. It's consistent and very pronounced - it happens in ever gear when downshifting or simply letting off the throttle.

I put close to 90 miles on it today (first ride w/ new pipe) and mileage was 65.1 MPG. I was getting 65-70 MPG with it bone stock. Wondering if it's too lean, but it's been jetted per DynoJet (stage 2) recommendation.

 

Air fuel mixture needs adjustment. The pro's here can chime in.

 

adjusted a/f best I could...still pops..

 

Popping is normal.

 

None of the above...

Your exhaust header may not be perfectly sealed. Try tightening a bit more.

 

Loosen all the bolts on the system. Tighten the header and work your way back to the muffler. If you still have excessive popping, go to 2.5 turns on the mixture. Aftermarket pipe is louder and the popping will never fully be gone. You can make it better though.

 

I got the advantage or some would say disadvantage of having fuel injection on my klx. I have done a lot of work to my bike with Cams & big bores etc. Whenever i've been tinkering with my laptop with the injection MAP to get best power vs best MPG & I go even very slightly lean, I get more popping. If I lower the fuel mix to gain as little as an extra 5mpg / tank full my bike will pop on deceleration....

in other words, you jets or injector balancing is on a very very fine line for power/mpg/popping! I don't think you are damaging your engine unless your running really lean. So my exhaust never has anything to do with popping & it does have a couple of super small leaks, that I really can't be bothered to fix. When it's running rich, no popping.

 

It wouldn't hurt to do a plug check to see if its running lean or not.

 

I got some minor decel popping when I put my FMF on. After I rejetted it was more pronounced. So I played with the mixture screw over a few weeks to get it dialed in. At first I got the popping to stop but was running a little too rich and having a hard time starting when warmed up. So I turned the screw back in a little and was able to get more reliable starting and the popping resumed. But it's pretty minimal and from what I've been told that's normal. So just play with the screw over a week or two and you'll get it dialed in.

 

My KLX650 only pops on decel if I have the throttle entirely closed, which is the pilot circuit which I've just never bothered to adjust. As for any throttle over idle, my personal experience and opinion over about 20 years use...

Dial-A-Jet

Read the theory and function then read the articles for media review. The Dial-A-Jet enrichener has taken in the world of ATV and snowmobilers, but never quite in the bikes. I think it's due to the old hard jet attitude. I've used one in my own KLX650 for over 10 years, compensating for a big bore, opened up air box, and a full exhaust. The plug color and pipe end color have been consistent regardless of temperature (18-100 deg F) and altitude (sea level at Daytona to about 5000+ feet in the Appalachians in WV). I've never changed a jet, only installed the Dial-A-Jet in the stock bike back in 1998 when I pulled the snorkle. The rest happened a few years later. It has compensated for mixture change without any adjustment, just as advertised. It's simple fluid dynamics adding fuel/air when there is a lean vacuum draw and being inactive when there is no vacuum draw. It's a lot like the Mikuni powerjet, but doesn't just flow raw fuel, but rather atomized air/fuel mix.

Way easier and no more costly than jet kits. MXA, Dirt Bike! and Motorcyclist back up the performance. Not to mention Dick's racing carbs.

But if you like to take your carb apart a lot, have at the jets.