Start with the basic's, replace your spark plug, make sure the bike has fresh fuel.

__________________
Click here to join the XT Supporter's scheme

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 /
[
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

I've already tried a new Iridium plug and it has had tanks of fuel through it since the problem started.

Im going to clean the fuel system, test the electrics and go from there. Might even take the bike back to standard spec to rule out a problem with the pipes or power commander.

Thanks for all your suggestions guys, looks like I'm in for a busy week!

You could always ask advise from a proper dealer.......not the idiots that say everything ok guv......and to me it sounds like electrical rather than fuel so coil/plug/plus leads etc would be my first port of call. Good luck!!

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(Now sold on, sob) 2011 Blue XT660X with gold wheels, was 26,500 km.
Engine mods: K&N Stage 1 filter, DNA Stage 2 filter, snorkel removed, Kev fuel mod fitted.
Plus: smoked Puig screen, Yam aluminium sump guard, Yamaha / Acerbis handguards, Givi Trekker aluminium side cases, Leo Vince X3 cans plus Kev front fork mod and Fender Xtender. Just fitted Michelin Road Pilot 3 tyres.

SOLD the XTX for a Super Ten 1200. And just bought a Raptor 700 so staying on here for some tips....

Cheers mate

I took the bike to my local Yamaha dealer (Arnolds in Burton) the first time and they said there is nothing wrong with it! To be fair to them no fault codes were showing and the bike was running fine when i collected it from them. I have a couple of hours spare now, so will check over the coil, ht lead and plug.

I would pull the tank off & check every electrical connector, pull them apart looking for corrosion, also check the main wiring loop that runs under the seat to the battery we have seen the loom rub through to the frame & cause short to earth problems.

__________________
Click here to join the XT Supporter's scheme

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 /
[
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

The loom looks fine to me. I do keep getting the fuel gauge flashing constantly since I put the power commander on, checked all the connections to it this afternoon and they seem fine. The underlying problem started way before the commander was added though.
I'm thinking of taking the bike bike to standard and going from there, at least it will eliminate the pipes, filters and PC from the equation. I've bought a new NGK plug cap and plug, just need a decent HT lead (any recommendations?). My plan is to ride the bike until it starts to happen, change the plug, cap and lead at the roadside and see if it helps. Cold and damp weather seems to increase the problem, I think it has to be electrical. Is it ok to put a bit of silicone grease in electrical connections to help keep damp out?

Thanks for your help Kev, this is really starting to get me down now!

Use a low suppressed HT lead, if I remember right I used a 2500k on my XTX instead of the standard 6500K ohm HT lead.

__________________
Click here to join the XT Supporter's scheme

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 /
[
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

My 2007 harley was fitted with 'race tuner' fuel management system. I started experiencing stalling and general rough riding conditions which required several expensive visits to the dealer for a variety of misdiagnosis. To make a long story short, the race tuner was faulty and once removed my problems disappeared. You may want to swap out your power commander, just to rule it out as the source of your problem. I wish I had done that $ooner.

This sounds to me like a fuel pump issue. I have a WR250R (2012) fitted with the later pump, and it fails intermittently with exactly the same symptoms as your bike exhibited initially. Most of the time, the WR runs fine, which means no chance of warranty until it fails completely.

Pumps do fail gradually at times, and my 250 is like this. A Chinese pump is in stock here at home ready to be fitted. I bought a spare Tenere one too. Total cost: about $90AUD.

The Chinese ones come with a new in-tank filter, too.

Regardless of what your issue is, I hope you get it sorted soon.

Hello buddies ..
I've got similar problems with my XT660Z.
riding at low speeds with the engine warm, the motorcycle begins to choke, failing losing acceleration. at some moments at high, 6000..6500 RPM she cuts without at least reaching 7000RPMs.
coincidence or not, soon began when I changed the stock exhaust for a LEOVINCE, and the only change was to close the injection of air into the exhaust to reduce the levels of carbon dioxide.
what do you think?

P.S .: excuse the English, I do not have socializing
best Regards