How do all,
These are my thoughts and feelings about my xt660z 09 so far...Overall I am happy with the bike, in the couple of months I've had it I've had to replace the head bearings and the cush drive rubbers, no probs easy enough, fitted kevs O2 and Fuel Mod as well as dna filter and snorkel removal...Now, like I say happy overall however I can't seem to get the bike to cruise at a set speed. so days are better than others I think its much better in the mornings then during the day.(I am HGV Driver so stupid o clock). Would the bike run better due to the colder temp in the mornings? I originally had kevs fuel mod set to 6oclock. I have blocked the AIS pipe as well and have now set fuel mod to 3oclock.

What I am seeing/feeling about the bike.
definitely a on/off feeling if I try to hold the speed at 30 in 2nd, 40 in 3rd 50 in 4th revs are about the 4000 mark.
clicking another gear 30 in 3rd 40 in 4th drops the rpm to around 3000 reduces the on/off feel quite a lot (but is still there)
The bike will pull in these gears but I feel its to high a gear.
I have also raised the idle to around 16-1700rpm this seems to have reduced the on/off feeling a bit so I am sticking with it for the moment.

I was also wondering whether its my riding style, my other bike is an FJR.

Sorry for the long boring post but trying to give as much info as poss

Did you find this feeling before you changed a lot of the intake and carburation aspects?
What condition are the cush drive rubbers in now?
Have you got the chain slack set right?

In all fairness probably didnt have the bike long enough before I started fettling.... cush rubbers are new with the added innertube ....drive chain ok

You've got pretty much the same set off intake/fuelling mods as I have and mine doesn't seem to exhibit the issue you describe? I do have a 2-1 and no cat though...

Have you tried all the simple stuff - throttle cables adjusted correctly etc? Are the cush rubbers you replaced still OK?

You could try Kev's twist grip mod, which will help with throttle control at small openings?

http://www.xt660.com/showthread.php?p=154983

Due to the nature of the way the fuel mod works (without getting too technical) its effects will vary slightly according the ambient temperature. At colder ambient air temperatures any given setting will have less of an effect on richening the mixture than at warmer temperatures.

For example, if you set it to "fool" the ECU into thinking its 5C lower than ambient at 20C for a richer air/fuel ratio, that exact same setting will only cause a "fooling effect" of 2.5C at an ambient temperature of 5C, so the air/fuel ratio will not be as rich.

The higher the ambient temperature, the greater the difference a given setting will make.

This graph might help you visualise what's going on...



I've found that if set right at an ambient temperature of 20C, that setting will generally cover most conditions from 15-25C. Below 10C I tend to crank the dial up one or two notches to compensate for the colder conditions and if its hotter than 25C (rare but not unknown in the UK), I back it off a bit.

It could be you've got the mod setup perfectly for the colder temperatures, but not for the warmer ones? Try having a fiddle with the fuel mod settings at different air temperatures. See if you can hang the fuel mod control out from under the seat so you can tweak it on the move easily.

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I have left my bike alone with regards to carburation modifications but I have had the choppy feeling and it was down to the cush drive rubbers a couple of times and the chain slack a couple of others.
For reference though given your speeds V gears I have always ridden 30mph = 3rd gear 40mph = 4th gear With the nature of a big single it's going to be choppy otherwise if you're trying to hold a lower gear.

I noticed this radical difference in the XTXs performance when the season changed.....and that is what made me fit the Kev fuel mod in the first place.

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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....

Cush rubbers plus innef tubes are new only month old...I think I have adjusted the chain properly. ...the only other thing that I am considering is replacing the iridium plug back to the standard...as I have read that others have had problems with them but with different symptoms (ie stalling, hard starting )

I found the iridium plug CR7EIX to be detrimental to the bike's performance.

It got horrifically choppy, and felt like unusual chain slack... engine pinking and basically struggling the whole time.

I have all the same mods as you.

Swapped to an iridium CR8EIX and the performance is better than ever.

Try this instead, or try a standard CR8E

Now the engine runs a bit hotter, thanks to the mods, a higher range plug seems to be the way to fix the problem you're having.

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Bike: 2013 XT660Z, TKC70 tyres

Mods:
Barkbusters, Scottoiler, DIY Tail Mod, DNA Stage 3, Power Commander V & O2 Eliminator, Exan X-Black Stainless exhaust, Tool tube, Ohlins linear front fork springs, Nitron rear shock, JT front and Supersprox rear sprockets, D.I.D. VX 520 chain, Adventure Spec bashplate, DIY USB Outlet, DIY chain guide, Kev's Throttle mod

http://www.facebook.com/onemooseonemotorbike

I have now replaced the spark plug witb the standard cr7e...one trip to and from work 16 miles each way....definitely runs smoother I the morning tha in the afternoon .but on off feeling has got much better.....going to run the bike for a week or two. ..stay tuned