Background: So after almost 2 years now of owning my 2012 ZX14R I decided to replace my stock exhaust with a slip on. I went with the slip on so I don't have to install a PC or ECU flash. I got the Brock's Alien Head and man its sweet. Deep rumbling sound that is awesome. Loud but not obnoxiously loud. I new about the decel popping of most of the after market exhaust and even with a slip on so I was expecting some. To my pleasant surprise it wasn't too bad and I frankly liked it. I also felt that the bike somewhat opened up at acceleration as if I gained a few extra horsepower. Not that I need more, but it just felt smoother.

15K Service: a few days ago I took the bike to the dealer for the 15K service. They found about 6 tight valves and adjusted them. I picked up the bike today and noticed that the popping increased specially when riding in the city and decelerating on 2nd gear. Also the bike seems a bit more restricted when I accelerate. It could be that I'm a bit paranoid because of the increased popping.

Question: do you guys think the valve adjustment has anything to do with the increased popping? Could it be other adjustments that was done that caused it?

Thanks in advance for your help!

Very interesting. I'm going to say NO, probably not. BUT-- The exhaust valves are always the ones that are tight. If they were tight before the adjustment and now loose after the adjustment, they are opening later and closing sooner. That could theoretically give you more exhaust restriction / less power. I'm saying, "theoretically" because valve adjustments to optimize intake/exhaust timing is one of those old racing tricks that probably no one can percieve unless they are measuring the results under race conditions. I believe I adjusted both intake and exhaust to minimum clearance. All exhaust were tight and I loosened them up the least I could to achieve safe operation. No perceivable change in power.

As far as the increased popping, I don't see how a change in exhaust timing would effect that. You're going to eliminate the same volume of exhaust no matter how much time there is to do it. It will happen over a brief interval if the valves are loose (open less time) or over an extended interval if the valves are tight (open more time). More time to eliminate exhaust seems optimum but it's the same amount of gas either way, just getting pushed out faster or slower.

If you had 1 or 2 tight intakes and they opened them up, that would give you less time for intake but just like the exhausts, it's the same volume coming in, just faster or slower. I don't see this giving you richer fueling which would cause the popping.

What could effect decel popping is that they cleaned your PAIR reed valves which need to come out to do the clearance check. Also, they may have cleaned up your T-bodies which likely were removed on a gen2 and adjusted the vacuum. Both of those are good things but I think the PAIR is the only one that would effect decel popping. The Tbodies are only going to let in as much air as your cylinders can hold just the same as the valves. I noticed no difference after doing my T-body vacuum adjustment nor did I notice a bit of difference after cleaning them (but it's nice to do it).

After all of that, I would say be glad that you have some evidence they actually did the adjustment. If the engine is not ticking badly, (come on, these babies do tick a little) I doubt you have cause to open the cover and check the adjustment. I doubt it's too loose. It should tighten up over time. Next valve adjustment, go in and do the feeler gauges yourself if they'll let you. I would be much less inclined to open the clearance up a whole lot after 25000 miles. The clearance will be tightening very slowly by that time.

DAMN!!! just about time to do my 3rd clearance check. 24k adjusted, 40k all exactly the same, 55k is right around the corner. Should be interesting.

I picked up the bike today and noticed that the popping increased specially when riding in the city and decelerating on 2nd gear. Also the bike seems a bit more restricted when I accelerate. It could be that I'm a bit paranoid because of the increased popping.

Paranoia it is!! :) I'm just going to go out and enjoy the bike. I can't get enough of the Brock's exhaust sound...lol

Thank you Rook for all the help man. I'm sure I'm speaking for more than just a newbie like me with limited mechanical knowledge. Btw, I also came across one of your postings in 2012 on valves adjustments. It was awesome visual and explanation. Excellent education for someone like me. Thanks again. It's greatly appreciated.

Probably was the Valve clearance adjustment tutorial. Glad it helped. Hope all pics were there because I have shuffled them around photobucket.

Did you block the pair valve deal in the airbox when you put the exhaust on? If not, thats more than likely whats causing it. If you look under the airbox on the left side of the bike You will see a good sized hose going into the airbox. Take that hose out and block it and seal the hole in your airbox. I actually just stuck a cap on the end of the hose then stuck it back in the airbox and the popping stopped.

Before removing my PAIR, I also had the clear air pipe plugged. I used a dowel and hose clamp to ensure it stayed in the hose. I have a tutorial on that. It seemed to reduce popping about 33% at best. From what I recall, the CANNON was just embarrassingly insane rolling to a stop even if I decelerated gently..

+3 for plugging the pair valve. Make sure you do that. However you will get a pop when the sub throttles close fully. I get one almost every time on decel around the 3500rpm mark. You can actually play with your fuel map and almost eleminate it totally with a bit of fuel in that range but you do not have any of that so... Just know it happens and why.