Hi all
I'd like to know what petrol everyone uses I.e normal unleaded or the dear stuff super unleaded. My dealer says just normal unleaded but the book says otherwise.

I use normal unleaded, however I know someone who used the expensive (more so) stuff and the ten didnt like it. It caused chugging and spluttering. When he changed back to normal fuel his ten was fine!

No idea if anyone else has found this though....could just be a one off, you know dirty fuel or something.

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XT660z......What a machine!!

Current mods:- Yamaha top box, Yamaha hanguards, Heated grips, High front fender, Aux lighting front/rear.

I use 98RON (or accasionally 99RON from Tesco) and find it to pull a little bit more cleanly between 2000 and 3000 rpm; less stuttering! The difference was apparent both before and after fitting a Kev mod and DNA filter and top. I'd guess that (as Kev indicates) that it runs a tad richer on 98 and it might help richen the closed loop fuelling a smidge?? Could be the placebo effect though! Interestingly my V8 Land Rover runs like a pig on 98RON, and my BSA likes 102RON (98 + octane booster).

As for bad fuel, it may be the case, I had a really bad tankful from my local Esso station (not a supermarket) two weeks ago (in the Land Rover) and it felt like the HT side of the ignition was breaking down, ran on any number of cylinders from 5 to 8 up to quarter throttle and ticked over like a lawnmower!

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Whatever's cheapest. Normally just 95RON. It's a big single donk, not a high performance engine. I'd run it on chip fat if I could

The reason manufactures recommend a fuel rating is the engine was tunned for the that specific RON rating, the ignition/fuel/compression ETC map was built to run on that rated fuel.

It is of no use building a fuel map on 98 & then run your bike/car on 95, the A/F ratio will be out.

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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 /
[
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 use 98 bp ultimate

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I went for a Dynorun some time ago.
The guy asked me to put higher octane in beforehand.
I'm assuming this was to get a better HP 'score', and that I'd have to put the same, more expensive fuel in from then on.

.... Just curious.

As I always just put the cheap stuff in.
When I go for my long overdue next dyno session I'll be putting the cheap stuff in, as I'm not worried about my HP on the dyno just the correct A/F bit.

Question: If using PC, would there be any HP gain from tuning a bike to run higher octane fuel - compared to a bike tuned to run on the cheap stuff?

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PCV REPLACEMENT ECU WITH 04 WIRING LOOM STAGE1&2DNA GEL SEAT INSERT LOWERED 20mm FRONT+REAR CLUTCH ARM MOD
FORKSPRING SPACERS TALLER SCREEN THROTTLE GRIP CAM MOD DISTANZIAS 46TOOTH REAR SPRKT
SPEEDO HEALER 30MM HANDLEBAR RISERS TOPBOX MOUNT 08 XTX SORTED, ALMOST.
...SHEEPSKIN - Because a pain at the rear is not just a moany pillion.

I was under the impression that the XT660 engine is designed for minimum octane rating of 95.

I run mine on 98, (BP Ultimate) and it gives no problems. I have heard of people having problems with Shells premium petrol, something along the lines of it being designed for cars and not bikes?? Never tried it myself...

Kev might be able to help you with more specifics. Cheers, Boneman...

The mapping on the XT660's have been designed to run on 95 RON fuels.

I once did A/F ratio testing between the different fuels RON ratings using the same brand of fuel & could see that the same bike running on 98 RON ran a bit richer than on 95 RON, the 91 Ron A/F ratio was leaner than using 95 RON.

There is a post in the modification index.

Engine & performance mods

19/ Different RON Fuels

__________________
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