2007 S4R constant throttle spit and sutter

[Drumagician]

Hi all, just hoping for some insight on the issue I'm having on my newly purchased 2007 S4R 998 with 6500 miles.  It has been upgraded by the previous owner with full termi exhaust, open air box with K&N (looks freshly cleaned), and DP flash to the stock ECU.  This bike starts flawlessly, accelerates flawlessly, decelerates flawlessly but at a constant throttle anywhere under 65 mph, it spits and sputters.  I believe it is running rich at constant throttle for a few reasons.  First, above 65 mph, it is smooth as butter, and it is probably due to getting more air crammed in from the faster speed, leaning the mixture out.  Second, this thing has been getting 25 (23-27) mpg on average.  I know these bikes suck gas, but this is pretty bad, which leads me back to the running rich thinking.  Some solution possibility options in my mind are...
-spend money on tuning software and adjusting the fuel map (Tubeboy probably)
-Replace fuel filter
-Change spark plugs and or plug wires
-Re-seat ECU plugs
-Injector cleaner
The bike runs so awesome otherwise, i'm leaning toward the fuel maping as the culprit.  If anyone has had a similar scenario, please help me out.  Thanks!

[koko64]

Fitting a PCV and a dyno tune is a costly but excellent way to get it all just so, with economy and smoothness at some specific throttle/rev inputs and power when you need it at others. Setting the TPS, idle mixture and synching the throttle bodies all contribute to a good tune.
Someone here with the same bike will chime in with some specific options.

[clubhousemotorsports]

KOKO is right that you should start with a fuel injection set up by someone who knows how. it may be the TPS is off and if you go playing with the mapping you have not fixed the underlying problem.

Buying the software is not a bad thing but start by making sure your foundation is sound.
Adjust valves
sync throttle bodies
set tps
set air bleeds

Does it still have the o2 sensor and or catalytic converter?  If it still runs an o2 sensor then at low throttle setting 4000ish and under rpm the bike is very lean, the o2 sensor will taka away any fuel you add as long as it is working as the factory intended. I see CO readings of .30 under 4000rpm on o2 sensor bikes and the bikes surge.

[Duck-Stew]

Check with whomever 're-flashed' the stock ecu.  Likely something got buggered there.  Mileage that I've seen on 998 powered Monsters is about 35-40mpg.  Plugs and fuel filter won't do it, ditto for re-seating ecu plugs.

[Drumagician]

To "Clubhouse", the o2 has been removed by PO. 
I'll also have to get with the PO about the flash.  All good stuff guys.  Now to just figure out what items I can do and what to leave for the pros. 

[Duck-Stew]

The air pressure/temperature switch could be damaged or unplugged.  That's what the ecu uses to determine what elevation and barometric pressure you're experiencing.

[clubhousemotorsports]

Without the O2 sensor it should run pretty well under 4000 right down to about 2500rpm's

As duck-stew said look at your sensors for something unplugged but that will not tell if one is bad.

As an FYI I have an S4RS in the shop now that is about to get a throttle position sensor as the one it has has failed, this has the effect of the throttle not telling the ecu correct information and the fueling map will be wrong. If you do not have the ability to test/check sensors i would get it to someone who can. If the map was good before and you have not done anything to damage the ecu (any wiring going on about the time this started) then a sensor going bad is a likely candidate so I would check them first.

[Drumagician]

Again, the bike runs very well throughout the entire rev range except for at a constant throttle; accelerate or decelerate just a hair, and it is as smooth as silk.  I really want to diagnose and tune myself whenever possible so planning on buying Tuneboy for this, as it seems to be the most user friendly.  Air pressure/temp sensor looks good.  As a test I wanted to lean out the air bleeds but it was already idleling at 1300 rpm.  Based on this, I think I'll do the entire TB calibration procedure.  Need to wait on the Tuneboy so I can do TPS reset though. 

[clubhousemotorsports]

Again, the bike runs very well throughout the entire rev range except for at a constant throttle; accelerate or decelerate just a hair, and it is as smooth as silk.

What you just said is pointing you to throttle position, when you get your tuneboy You will find out that the throttle position is often low and this is where bikes tend to be lean often. Too rich and throttle response suffers too lean and the bike surges. No O2 sensor should be richer in this zone but you might find it is not right for your bike.

Be sure to check your TPS to make sure it does not have a dead spot in it. If it does not react in a liner fashion you may have a bad TPS. The problem you will face with tuning will be  not having a way to easily check your progress without test rides. I used to tune while riding with a FIM box taped to the gas tank so I could adjust while on the road, hard to do with a laptop.

Make sure all sensors are correct before touching any maps, if you adjust the map around a bad or failing sensor you will be chasing your tail.

[Drumagician]

How do you check the TPS for bad spots? Also I follow you about the throttle position being lean or rich but the throllte response is perfect and there is no surging, only spitting and sputtering; not sure how else to explain it.  I am slowly working through sensor verifications. 

[Drumagician]

So here is some feedback for anyone interested...
Just completed a full maintenance on my bike including changing valve shims to the newer specs, TPS reset, throttle body sync, timing belts changed, checked for vacuum leaks, etc.  Still had the same spit and sputter with a constant throttle cruise.   I downloaded ScanM5X on my phone and got the Wi-Fi OBD2 and fiat cables; the TPS reset was done with this app as well.  Went for a ride and adjusted the CO trim incrementally from the initial +38 downward until the spit and sputter went away; this landed me at +5. Bike runs perfectly now!  Now I started thinking that reducing the trim this much may have caused a lean condition in the higher load/throttle positions that may not be noticeable to me.  So I contacted David at Rexxer which is where the stock ecu was flashed hoping for some input.  He said the CO trim only has effect at idle and just off idle.  This is contrary to everything else I have read and that my CO trim adjustment just fixed my problem.  Anybody have any insight on this?

[Howie]

CO trim's biggest effect is at idle and decel closed throttle (popping in exhaust)  As throttle opens or load increases there is less effect since air flow is so high.  It is possible that CO trim could effect cruise if throttle opening is a very small angle, as in off idle and the program is very close to too lean.  My advice is just go out and