This info may be of no interest to anyone but I thought I would share my finds anyway.

I have been doing some testing with different RON fuels to see the effects on the XT660 Motor A/F ratio & was quite surprised with the results.

I loaded a zero fuel map in my power commander & built a custom made fuel map running my bike on 95 RON fuel the recommended fuel octane for the XT660 & set the A/F ratio at 13.2:1 across the whole fuel map.

After building the custom fuel map for the 95 RON fuel I then switched to E10 10% Ethanol 91 RON fuel, I found my bike ran leaner by 4% across the whole fuel map, compared to the 95 RON fuel.

I then ran my bike of 98 RON fuel using the same custom map for the 95 RON fuel & found it ran richer by 3% then using 95 RON fuel.

So the morel of the sorry is if you dyno tune your bike on 95 RON fuel for example you need to use this grade of fuel all the time, otherwise your A/F ratio will be to lean using 91 RON fuel or to rich using 98 RON fuel.

The XT660 is supposed to run on 95 RON fuel, so the boys worried about running your bike lean should use 98 RON fuel as it will run richer by 3% then using the recommended 95 RON fuel.

My XTX does run on 91 RON fuels but I had to build a custom made fuel map to get the A/F right, I would not run it with 91 ron fuel long term, the bike did not ping after I made the custom map.

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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