Ok I searched the forum and looked for popping noises, the search came up with many different answers so I though I would get my answer but the thing is...all the quads that "popped" or "sputtered" were ALL modified and the jetting was off, and my quad, an 04' z400, is completely stock until the end of this weekend I'm planning on getting a K&N Filter and most likely a Full Yosh Pipe along with some other mods...so when I'm decelerating and it "pops" does that still mean the jetting is off somehow? If so should I just wait to go to a dealer or is it easy to adjust (never done it...but have a basic idea of what to do)? And a lot of people said it was coming from various places, mine is from my exhaust pipe...so mabye it's just the stock pipe? Or the carb? Any help would be much appreciated.

Thanks!

 

Most popping I've heard from decellerating are normal, if it's from the exhaust pipe. Does it do it mainly at higher rpms or when going down a hill? It's perfectly normal if that's the case. Now of course your jetting will be way off w/ a filter and yoshi. Good luck.

 

If you go to the mikuni carb website...youll find this.

4: Backfires in Exhaust

Note:

It is normal for many high performance exhaust systems to moderately backfire or pop when the throttle is closed from mid-to-high rpm. In fact, one should expect a well-tuned high performance engine to "pop" and "crackle" when the throttle is closed at high rpm.

The popping is a result of the air/fuel mixture becoming very lean when the throttle is closed and the engine is rotating well above idle speed. It is also necessary that the exhaust system have rather open mufflers.

Why This (normally) Happens:

1) When the throttle valve is in the idle position, fuel does not flow out of the main system (needle, needle jet, main jet). Fuel is only delivered to the engine by the pilot (idle) system.
2) The combined effect of the closed throttle and elevated engine rpm is to create a fairly strong vacuum in the intake manifold. This vacuum, in turn, causes a high air flow rate through the small gap formed by the throttle valve and carburetor throat.
3) Under these conditions the pilot (idle) system cannot deliver enough fuel to create a normal, combustible air/fuel ratio. The mixture becomes too lean to burn reliably in the combustion chamber. It gets sent into the exhaust system unburned and collects there.
4) When the odd firing of the lean mixture does occur, it is sent, still burning, into the exhaust system where it sometimes ignites the raw mixture that has collected ---- the exhaust then pops or backfires.
5) Completely stock Harleys do not do this until open-end mufflers, such as the popular Screamin' Eagle slip-ons, are installed. The exhaust must be both free-flowing and have an open exit for the popping to occur.

Other possible causes:

Air Leaks:

Any source of fresh air into the exhaust system can create or worsen the conditions that bring about exhaust backfiring. The most common entry point is the junction of the header pipes and mufflers. Even a small air leak can dramatically increase the intensity or likelihood of exhaust system backfiring.

A high temperature silicone sealant, as can be found in many auto parts stores, may be used to seal the pipe/muffler junction.

Lean Carburetion:

While exhaust system popping may be considered normal, it is certainly made worse by an overly lean idle circuit.

Be sure that your carburetor's pilot jet is the correct size and that the idle air mixture screw is correctly adjusted before looking for other causes of popping. The procedure for adjusting the pilot circuit is covered in the Tuning Manual.

Ignition:

If exhaust system popping is very loud, irregular and accompanied by loss of power, then you should suspect that the ignition system is not performing as it should. If, for some reason, the ignition sometimes fires at the wrong time, then exhaust popping can become very energetic (loud). Look for failing high tension leads (plug wires), failing ignition coil(s) and especially switches or connectors as possible causes.

So some poping with an open exhaust is normal, but if its totally stock, its not.

 

Hmm...well now I'm kind confused hahaha. Ok, currently I'm completely stock except for a horn and some other little things. I ride a ton on the road, so I ride about 1 mile and I'm drving about 25-30mph and I come to the stop sign and I decelerate and downshift, but then I hear the popping noises...That's all though, no loss of power, no wierd thing's happening, nothing. My birthday is coming up in about...5 days (June 2) so I'm getting a K&N Filter/PowerLid, White Bro's Carbon Pro Exhaust, DynoJet Jet Kit, Mabye new plastics, and some other stuff I'm not sure I want yet...so after I add the new exhaust and rejet it and all that fun stuff I don't think I will have to deal with this prob anymore...hopefully haha...well I'm going to go ride some more so thanks everyone for the help!

Kris

 

A quick and easy check, to see if its too lean, is to pull on the choke, as you let off the throttle. If it stops popping, then you know for sure its a lean idle circuit.
If its all stock, and there are no intake or exhaust leaks...then try 1/8 to 1/4 richer on the mixture screw, and that should stop the popping.