backfiring s2r

[SILENTCOREY]

I am having a problem with a popping sound coming from the exhaust on decel, it almost sounds like a backfire. The only mod I have done to this bike is a K&N air filter(drop in factory style replacement). All maintenance has been done regularly, oil changes every 2500 mi, valve adjustment at the 6k interval, and timing belt adjustment at the same time. There doesn't seem to be any exhaust leaks, or fluid leaks of any kind, also theres only about 8k on the bike. I don't really ride it hard, I do a lot of 2up riding, and basic commuting. It doesn't seem to do it every time but if I do happen to go above the 6k rpm mark and then decel it will pop.

I'm wondering if the air filter is the problem or if it could be a fuel filter in need of replacement.  Would the air filter cause this? Do I need to have the fuel system remapped for this tiny mod? I have a hard time believing it would be running too lean just from a filter change.

By the way the bike is an 06 s2r 800.

I do appreciate any help or advise you give.

[Speeddog]

The bikes come from the factory very lean.
The K&N may have leaned it out  tiny bit, and it was enough.

If you've still got the original air filter, put it in and see if the popping goes away.

[SILENTCOREY]

I do still have it, Ill try that when the weather clears up

thanks

[Monstermash]

I do still have it, Ill try that when the weather clears up

thanks

And when you find out that is indeed the problem, please send the K&N filter to me so it will never happen again! 

[SILENTCOREY]

So I put the oem filter back in last week. Result, symptoms are better but not fixed. I wonder if it needs more time to adjust because I've only gone about 45mi since the change. Does it make small adjustments with time and changing environment or is it just set at the factory and thats it? Either way I think I'll recheck my valves and look for exhaust/vacuum leaks. I think if I don't find anything wrong with it I'll find a device to do some fuel tunning with and get new exhaust, and open the air box. I figure might as well while going through the trouble of fixing this small problem.

Does anyone have suggestions on products for fuel tunning?

[jammer]

If you're sure it's not exhaust leak, have you pulled your plugs to see?  White = lean, dark = rich.  Though I suspect it might be white, ie. engine is burning hot and popping.

This problem has been discussed at length, on the other forum, and it's starting to be discussed here as well.  Though, if I remember correctly, it affected the S2R1000 more than the S2R800.

Some solutions are:

Dealer adjust the AFR as best they can, but it's not perfect.
Rapid Bike (I'm not plugging the product as I have no 1st hand experience), and the dealers are members here;
DP ecu, either alone or part of the exhaust kit;
PCIII (Power Commander has a model listed for the '03-'06 S2R800.

[monster monkey]

I've noticed the same thing on my S2r1k, which is bone stock. I just chalked it up to the endearing characteristics of a monster.
let me know if you find a resolution, if any.......

+1 on the post

[A.B]

My S2R 800 does the same thing.  Ive been running with just the udder for a couple years now, and it just started doing this last week.  Can you adjust the A/F with out taking it to the dealer or buying a PCIII? 

[clubhousemotorsports]

When you on the decel portion of the map the fuel mixture may be too lean.
start with the basics first
110% sure no exhaust leaks
efi set-up properly
no new changes like you just opened up the airbox or put pods on

The issue is that you are at high rpm with the throttle closed and air is still being jammed in the airbox. this leads to a lean condition. The fuel map has a provision for decel just for this reason but it may not be correcting enough. Try richening the air screws a little and see it it helps as this will richen the closed throttle portion of the equation. some times a little richer TPS setting will also do the trick.
Good luck

[SILENTCOREY]

How might I go about finding said screws, and which direction should I turn them? as well as how much? It would be nice if I knew what I was looking for instead of just assuming.

I am a carburettor mechanic on the side, mostly on cars/trucks but I do most anything, so for the most part I do understand the basics of a throttle body and an efi system. I just really don't want to cause any fueling problems. Any help would be appreciated as I want to fix this as soon as possible. One because of my concern for my bikes mechanical state, and two because its embarrassing to be popping and backfiring when riding spiritedly with fellow bikers.

I was also just thinking the other night that maybe I could've gotten some bad gas and partially clogged the fuel filter, but I would think if that were the case it would run lean, or quite poorly all the time. not just on decel. I am going to replace it this weekend when the tank is empty anyway just to make absolutely sure thats not an issue.  I will also check and replace the plugs and recheck for an exhaust leak.

I have ridden the bike for a week now and haven't had the problem but its all been commuting back and fourth to work so no real spirited riding to speak of. I am certain it will do it if i just get on it. but thats just not my normal riding style. At least not for the daily commute.

[Speeddog]

The air screws are on the sides of the throttle bodies, in a little 'well'.

The well may be covered with a grey plastic plug.

Turning them in (clockwise) reduces the airflow, so it richens the mixture.

[SILENTCOREY]

thanks speedog! i looked at it today and assumed that was it. i havent had much time to let it cool down enough to work on it, since i just got home but i will in a few. i tried to get it to backfire on the way home today and it didnt do it. i highly doubt that it would just fix itself but i do have the factory paper filter in it. its been in there for a few weeks now. i wonder if it just had to learn the different airflow.

well its been my experience that mechanical issues just don't fix themselves. they usually just hide and become bigger problems later on.

thanks everybody for your replies. this has been very helpful.

[SILENTCOREY]

So its been a while and I figured its time for an update. Since my last post I have readjusted the air bleed screws on the throttle bodies. I found they were turned out one and three quarters turns. In doing some searching on this forum I discovered that the best adjustment for them is about three quarters turn out from bottom. The backfiring issue got a little better but didn't disappear. So the only thing left to check before taking the bike in to the dealer was the valves. 

When I checked the valves all the openers were perfect but two of the closers needed adjustment. The exhaust horizontal was off by .0015 and, the vertical intake was off by .002 . So reseting them back to .oo1 and putting the bike back together seemed to fix the problem. I did this maintenance at the 9k mark and I couldn't believe they were off that much.

Anyway for about the next 525 miles its been great. No sputtering or backfiring on decel like before until today on the way home from work. I got tired of following this old guy in a little pickup so I pasted him on the highway. Starting at about 55mph in sixth gear and accelerating to about 80 and then back down to about 65mph in the same gear. A soon as I slowed down to 70mph it backfired just like normal.  The ambient temp was about 95 in the sun and the oil temp gauge was at about 180.  Now this is the only time that its done this since but I have to say I'm a bit concerned. The only other thing I may try is to unhook the battery for a little bit to see if it does it again. I'm just wondering if the ecu is learning to lean out the afm, and by unplugging the battery erasing this learned map and defaulting to a factory preset one. Thus enabling it to run a little more rich than necessary. The reason I'm thinking this is the last time I disconnected the battery for some maintenance the problem disappeared. If you've ever done you own valve job you know that you have to remove the battery and tray to get to the vertical cylinder valve covers. So I'm thinking that may be the issue and I might just have to shell out the bucks and buy the power commander and have it tuned by a professional.

I have alway been taught not to modify something in order to get more power from it if it's not running properly in it's factory form. So keeping that in mind does anyone out there think I'm way off base and the battery thing is  a waste of time? Should I just bite the bullet and take it to a dealer to have them futs around with it? Or should I just buy the pcIII and have it tuned by a professional? Any opinions would be appreciated.