My guess diagnoses it as a "muffler crack". It happens with a lot of aftermarket muffler/exhaust systems....There's nothing wrong with it, just annoying to some people. I actually prefer having a crackling muffler
On the other hand - it could be backfiring? Idk enough about these ninja's to make that a fair assumption.
wow, after doing some searching, I couldn't find anything... I know we've covered this a bunch before, so I'll just restate the known problem.
This popping you're describing can be the result of a lot of different things.
-kleen air system recycling oil vapors into the intake
-leaky exhaust valves
However, more than likely you're "problem" is that the main jet is slightly too rich, and the popping is unburned gas exploding in the exhaust system. It was probably this way from the factory but the stock exhaust is so quiet you didn't hear it. With the new slip-on it's much easier to hear.
It's not going to damage anything, and is no cause for concern. If it bothers you, I recommend you take it to a shop and ask them to dyno-tune the bike, and even then, it might still have it - just a function of carbs in general, especially a CV carb. You could also conceivably tune this pop out of the exhaust, but it might be dangerous in that you're going to have to go quite lean to achieve that, which could lead to a burned valve, but that's all in an extreme case scenario.
I personally like the sound, because it's very much like race bike, but you might be different. What would you like to do with the sound, and maybe we can provide some more options?
NOTE: Posting in 2 different places on the forum, about the same thing is a silly way to get a reaction...
thanks spooph and jtgrenier, for advice like u said i dont mind the poping , just hope im not hurting the bike,like u said spooph, if it wont hurt the bike then i wont worrie about it..it only has 1800 miles......but man with the slip on it can really punchpower in low mid range...