1)I have this problem that my fuel consumption is so bad that i get max 200km out of a full tank(15l), i then have like 3-2litre in the tank.
i run stage 3 airbox, full leovince exhaust, PC V with a map from the forum according to my mods.

2)Sometimes when i pull real hard my bike stumbles once and picks right back up, i wonder what this is, is this a fueling or a clutch problem?

3)My fuel light on the dashboard lights up when i still have 7-8litres of fuel in the tank, is this normal or not? i think it is not logical.

xt660x from 2005 with 14k kms on it

My first thoughts are that you should try a different PCV map. Sounds like its running too rich in most areas.

Which map are you using?

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2004-2007 Yamaha XT660.R European model
AKRAPOVIC OPEN SLIP ONS
DNA STAGE 3 AIR BOX KIT

Is the one i am using, before i had the stage 3 airbox i had the same problem, i took a map according to my mods and again it was way to rich
i have a db killer in my exhausts

First thing I'd do is go back to a suitable Stage 2 map and see how things pan out.

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Ok ill try it, how to see if its a good map? Only by the color of the sparkplug?

You got any idea about the fuel light going on to soon?

Try the Stage 2 map and see if it's any better. If it is then I'll have a look at the fuel trims in the two maps and see if there is anything obvious. Looking at the spark plug will give you a very rough idea of what's going on with an air/fuel ratio but with modern fuel containing ethanol they are much harder and less reliable to read as the fuel additives leave odd coloured deposits even if the engine is running well.

As for the fuel light... they all do that! They are unreliable and inconsistent (the fuel gauge on a Z is even worse) and should only be ever used as very rough indicator that the fuel level is dropping. Best just to reset the trip and get used to how many Km you can go before you need to fill up.

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Ok ty i will try it.

Even worse? Wauw. Yes i use the trip meter, cause i din't know if the light was reliable, i know its not now, thank you :-)

ON mine thelow fuel light comes on when i have used up about 10L. But depending on the slop, (uphill or downhill) this can fluctuate (on/off). I guess it is caused by the shape of the tank and the location of the sensor.

Why it comes on with 1/3 tank still full, I don't know maybe the wisdom is if you are on a long distance adventure trip, you have plenty fuel left to get to the first available station

I don't understand what mapping is can you explain please?
I have just fitted a fuel mod and o2 controller and my bike xtx has started cutting out and responds slowly if i rev the throttle fast what can i do as the bike seem worse than before i fitted them????

As per PM Steve can you reduce your CO1 in your dash from your setting of 22 down to 5 & make sure your idle speed is set to 1500rpm when the motor is at operating temperature.

Having our CO set to 22 then adding an Adjustable fuel mod which add more fuel again will make the bike run too rich.

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Mods that I have done to my XTX's

My 04 XTX
Stage 1 & 2 DNA filters / Kev fuel mod / snorkel mod / Drilled air box mod / Engine breather mod / Fork Spacer mod / 15w fork oil /
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My 07 XTX
Raptor 700 cylinder 102mm / Modified Crank Case to take a 105mm Raptor Cylinder / 11:1 102mm JE Raptor piston / Stage 1 Raptor Hot Cam / Ported head / Colder Spark Plug / +2mm Throttle body / DNA stage 1 & 2 filters / Modified Air Box / Snorkel removed / Worry Brothers stage 2 filter cover / 6mm & 8mm Bolts Replaced with Titanium Bolts / Recovered seat in Black / O2 Eliminator /

My 09 XTX
59HP at the rear wheel / Stage 2 Raptor Hot Cam / DNA stage 3 Air Box / Carbon Can Exhausts / Modified Exhaust Link Pipes / PCIII With Custom Fuel Map / Wideband Commander O2 Data logger / LCD100 Dyno Jet display & fuel adjuster / 2500 OHM HT lead instead of a 10K OHM XT lead / Extra Coolant Cooler / Protaper Fat Bars / Tail Tidy With LED Tail Light / OKE Protection Knobs / LED indicators / AIS blocked / Modified rear sprocket rubbers / Rear Foot Pegs removed / 09 ECU With 02 Sensor Changed To A 06 ECU / Complete wiring harnes Changed from 09 to 04 / Home made LED resistor flasher / Hole drilled in the fuel tank filler neck to allow quicker filling / Modified Bar End Weights / Progressive front fork springs, 15W fork oil, forks lowered 25mm, used XTR rear links lowering the rear 20mm, rear spring one click stiffer / Changed front & rear guards from blue to black / 47T rear sprocket / Speedo Healer V4.0 / Kev throttle cam mod / Throttle grip mod / The new 2010 O2 sensor mod is out, works a treat, The new 2012 O2 Controller is out, PM me for details

Now ride a 2018 MT09SP ABS + TCS

My KTM 990 SMR Mod book. http://www.ktmsmt.com/viewtopic.php?f=13&t=4946