flat spot

[idh959]

guys,

I'm experiencing a flat spot around the 4-5k rev range, use to be at around 3k. Fugged thing is I had it serviced only 3000km's ago at kwaka parra. I've just cleaned the air filter, gone through a can of motul fuel system cleaner and no change. Any ideas what I should be looking at next? bike sounds normal. I always run castrol or BP premium.

98 zx6r.

[Felix]

If it is a carbied bike, then I'd be looking at getting them overhauled, as it is most likely a fueling thing. Needles and seats top of the list of things to replace, and note that wear on a needle that causes a flat spots may not be noticeable to the naked eye, but also the internals of carby's can gum up some of the vacuum passages etc, so a good clean out not a bad idea. While you're at it, probably time to replace all the fuel hoses and filters.

If it is an injected bike then probably time for the injectors to be ripped out and cleaned and tested by an injector cleaning specialist.

Probably the strongest clue is that it "used" to be 3k and now is 4-5k - it is getting worse, rather than shifting.

[Aussie Ninja]

All '98 6Rs come with that little flat spot at 3 grand. 4-5 is at the start of the main circuit. Someting stuck in the slider vacumme ports? Check their action and see if they all open about the same if you give it a rev. If the fuel level in the carbie bowls is too low there will be a big lean spot, but if thats the case then there should also be hesitation just as you open the throttle in a cruise. I would expect to find the fuel paggages in you carbie spotless after the motul. Hmmm.....

[idh959]

thanks for the tips guys, I think the mixture is ok, no hesitation on throttle. However, where are the slider vacumme ports? according to the carby diagram attached.

[AussieZed]

Have you checked to make sure that the aircleaner lid is properly sealed / seated ?

Sounds more like severe lean condition rather than a partial blockage.

[Aussie Ninja]

thanks for the tips guys, I think the mixture is ok, no hesitation on throttle. However, where are the slider vacumme ports? according to the carby diagram attached.

See 6 on the pic? Go left a bit and up a bit. See that tiny O ring? Thats the slider vacumme, its internal in the carbies. I think AussieZed may have someting. During a service there should be no reason to pull apart the carbies so look for things they would have had off and have possibly stuffed up. Mabye a vavumme line is off or they didn't tighten one of the carbie manifold clamps.....