Hi all.

Just bought a used '05 XT660X and have few questions.

1) CO is set to 80. But there are no any mods installed on the bike. Can 80 be a normal value? I think previous owner could change it to get "moar power" Should I set it to 0? I tried to do that and engine works "different", but I don't know what is "normal" work Any advice will be good.

2) Have strange symptom: if accelerate to some speed and then keep it unchanged (e.g. 30mph) I get abrupt loss of power after few seconds. For example:
I put 1st gear and start to move. Give some throttle and switch to 2nd gear. Then I need to keep my speed constant so I just fix the throttle on some level. But after few seconds of such a ride I feel something like sudden loss of power - engine suddenly drops it's revs for about 1/4 from origin value and so I feel a abrupt loss of speed, which is very-very uncomfortable. After this I need to give more throttle to get my speed back, but feelings are like engine really lost it's power and accelerating much slower. I am facing this problem on any gear and any speed, but seems it occurs only when I am trying to keep the speed constant for a long time, not accelerating. Playing with CO doesn't help.


3) And the last problem which can be related to the previous one:
If I give some throttle for a short time on neutral gear - engine keeps high revs for a few seconds after I released the throttle before return to idle revs. Playing with CO doesn't help.

Will be happy to get any help. This bike is really rear in my country so I can get help only here, on this forum


P.S. Sorry for my English.

Welcome mate.

Seeing as its an 2005 XTX, start by having a read of these two threads first...

http://www.xt660.com/showthread.php?t=519

http://www.xt660.com/showthread.php?t=8546

BTW - Your English is very good!

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Don't apologise for your English, it sure beats our er Russian or whatever hehe!!! You sure need to read and study all of the information on here. You have the classic XT660 symptoms and you can sort them out no problem but you must go step by step. In other words, write down your starting point. Then change ONE setting and try the bike again and write everything down. OK???? Ciao Simon

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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....

Thanks for your attention guys.

I have old ECU (version 00). I have contacted Yamaha dealer but they couldn't help because XTX was not officially supplied to my country.

I have played with CO in 0-80 range. And I can really feel the changes, but they are too complicated to describe. The only thing I can say that engine always have this "suddenly loss of power" after few seconds. I can see the word 'surging' (am I correct?) everywhere on this forum, but I can hardly understand what does it really means

Other thing I am worrying about is "revs are higher than idle for few seconds after I release the throttle". This thing occurred just a few days ago, so I'm afraid this is not related to ECU fuel maps or something. Looks like this can be related to "mass air flow sensor" (don't know how do you call it) or some intake air leakage or other mechanical problem.

And sometimes engine could just stop while I'm switching between the gears (was 2 times only, but anyway).

So the thing I am asking for is to tell me which of my problems are 'XTX native' and which are not normal. Don't want to kill my bike, but don't want to make panic without a reason as well

This is my second bike, and I haven't had such kind of problems with my old one. That's why I'm nervous.