Just purchased 2006 SW, with 13K miles, previous owner installed K&N airfilter and I noticed when I realease the throttle there is a pop in the exhaust. The question I have is should I remove K&N filter and install OEM filter? Or do you think something else should be done?


Thanks in advance

The Pop in the exhaust can be caused by the K&N but it is not sure that it is caused by the K&N. It is also possible that it is normal...

I'm not sure, i also have a K&N installed and i also have the pop. But i think i also had this with the stock filter, but i'm really not sure...

But why do you want to change the filter or do some other maintenance? It is no technical problem. It is a normal behavior caused by unburned Air/Gas in the exhaust. If you want to eliminate this under ever condition, then you have to missadjust your engine (and also lost power) because a correct adjusted engine will do this under some conditions...

Or add a power commander which will readjust the fuel/air ratio for more power across the entire acceleration band...

Have you checked the K&N to see if it needs cleaning. Popping does sound like you have a fuel to air misadjustment. The K&N is a top quality filter and should not create a problem on its own. Check your plugs too. There are other simple steps to try as well.

Good luck.

But also with correct adjusted engine it is normal that unburned fuel comes to the exhaust if you close the throttle from high rpms very fast...
Sometimes you also have a flame out of the exhaust.
You have this more with a carburettor but also with fuel injection...

You HD experts will know if it is true or not... I have heard that the rumble of the HD comes from mis-timed engine. If that is true, the purr of the Wing must come from purrfect timing.

There are 3 ways to burn fuel in the exhaust:
First mis-timed engine or exactly valves
Second: "false Air" (so we call it in germany), that means a "leak" in the exhaust that fresh Air can be sucked in the exhaust in combination with unburned fuel
Third: for better filling of the combustion chamber the valves are a little bit longer opened than realy needed (and there are not mis-timed)

The third case in combination with very quick closing of throttle at high rpms or in combination with a K&N Filter or in combination with an open exhaust or ("worst case") a combination of this will also cause the plop and it is normal. If you ms-time the valves that this will not happen, then you lost power...

Sure, there are some other possibilities to get fuel in the Exhaust like "bad" mapping, aged/bad spark plugs but you need Air and fuel in the exhaust for the plop and the Air will come from one of the ways above.

Normaly it is the third one, and this is normal...
If it is not the third one, normaly you will hear the valves or the leak...

First thing I would check for is an Air Leak in the whole system from the filter to the last join in the end can.

The easy way to trace it is to spray each individual connection with WD40 - ONE AT A TIME - and run the bike up. Once the poping is no longer evident you can then set about fixing the leaking joint/seal.

Don't forget the obvious like a bent air box lid or a damaged seal either.

I had a real pain in the ass problem from this on a CX and it turned out to be one of the carbs not seated properly in an inlet rubber which wasn't visable unless you checked it with a mirror!

I really do doubt its the K&N on its own as they are specifically designed not to do this sort of thing.

Thanks everyone for your responses, I'll take the filter out and clean it and oil it. Do I need the K& N kit for that? My friend thought the OEM filter would stop the pop. Not sure how old the plugs are, might replace them also. My friend has a sw and he drove mine and claims it seems to run a little faster than his, which at my age is no big deal.

Spike