Frankly I've gotten some decel popping on just about every 4-stroke single with a pipe, jetting, and airbox mods I've ever owned. I jet for clean, crisp response and maximum fuel mileage without being too lean. One of the reasons for decel pop with these mods may be a kind of scavenging effect that occurs when you have improved intake and exhaust efficiency. This is not really a performance or damage issue under these conditions. Here's one of the best articles I've ever seen on the issue. You folks who are trying to remove this issue with richer jetting may be screwing up the overall performance of your fuel delivery.

Popping on Deceleration - ThumperTalk

 

Plug looks pretty good to me... cardboard brown on the electrode, graduating darker (to dark brown/black) on the side opposite the electrode. Insulator is clean and white like a brand new plug.

Might be a tad lean... I'm going to try to turn the air/fuel screw out another 1/4 turn, and see how that works.


Hmmm... Just adjusted 1/4 turn out. Haven't tested it yet, but it *did* make me wonder what all the whining is regarding the Kouba Screw. Really!!!??? It took me a whole 3 seconds to make the adjustment with a 1/4" flat blade bit. No pulling the carb, no moving anything... just stick the bit up there and turn it by hand. With all the ruckus people make over the Kouba Screw, I thought it was going to be difficult to make the adjustment *without* one. Not so!!!

Anyway, I think I found the exhaust leak. Seems the front joint where the pipe flare connects to the can is passing quite a lot of exhaust gases right there. I thought I'd find something at the slip-on joint, but it turns out it's further back. Not sure what to do about it, since that's where it comes apart to re-pack the muffler. I could seal it, but I'm more likely to just leave it alone.

 

I thought dynojets instructions for stage 2 was 128 jet and 2,3/4 turns out. That's about where mine is without a snorkle and I have no poping on decel, none, nada. It was by accident though as I just followed the instructions and all was good. But I would'nt lose sleep over it as most bikes with a custom exhaust pop some on decel.

 

You used the default DynoJet instructions... I emailed them prior to receiving my kit, and asked specifically about setup for 4,700-10,000 feet above sea level. I'm using the setup they recommended for the altitude I live and ride at.

My setup was perfect until I installed the new muffler. I think I'm going to email them again and see if I should make changes to compensate for the new pipe.

 

I can just about guarantee that you need to up the jetting with a good aftermarket pipe...and maybe even raise the needle. Taking the recommendations of DJ or someone else is a good starting point, but you usually need to come to a final and proper jetting conclusion with some experimentation on your own. You mentioned reading a spark plug. I'm surprised that you can get any substantive reading on a spark plug with today's fuel. Usually correct jetting is arrived at by driveability, throttle response, lack of detonation, and decent fuel economy. Yes, it takes a bit of putzing, but perfection always does. You've noticed how every one of these bikes isn't exactly same by your observation on the stater jet issue. So don't expect them all to always require the exact same jetting.

However, the jetting mods in the range for addressing a performance pipe don't usually affect the issue of decel pop. The throttle is usually shut when most decel pop occurs, so the idle circuit is the main area of concern. That said, as you could see from the article, it's a bit of the nature of the beast when modding the intake and exhaust. Some even comment that decel pop...within reason...is the sound of clean running and fuel efficient operation on bikes like ours.

 

Yep what Zomby said....+1

 

When I downshift, it pops like a 2-stroke! I kinda like it...

I shot off an email to the DynoJet folks. Seeing as they got it PREFECT the first time, I'm gonna hope for Two-for-Two! ;-)

I understand that there are differences in bikes. However, these guys engineer the kits to be bike specific, and they have a great deal of expertise under their belts. The setup they first sent me was WILDLY different from their stock setup, but yet it was incredibly SPOT ON! No fiddling necessary. If nothing else, they will give me a great starting point, and I can adjust things from there.

One of the reasons I paid extra for the DynoJet kit (over just buying stock Kaw parts) was I was buying their expertise and customer service. So far, I have not been disappointed.

 

So because mine doesn't pop it's abnormal? Do I need to be concerned?

 

Didn't mention if you have an after-market exhaust...

Mine never popped *UNITL* I installed the DEP pipe.

 

Didn't the link TNC posted mention you will never get accurate results in deminishing the popping if you are not absolutely sure you exhuast is not leaking... It was a good arguement, the fuel needs air to pop, and its most likely comming from a leak.

I'm not saying that by eliminating the leak, you will for sure eliminate the pop... but if in fact you do have a leak there will always be some poping unless you over richin the idle circuit to extreme measures to cool the exhaust to falsely hide a pop.

If in fact though you do have a well sealed exhaust, then you may still as well have popping... maybe due to not enough/too much fuel in the idle circuit to delay any combustion until it reaches the hot exhaust there after with its premixed oxygen...

Just a thought...