GSX750F Rpugh Idle and flat spot

[Wonko]

I have a 2 problems with how my bike runs and they might be interlinked.

First one is when it's idleing. Intermident problem happens about 70% of the time. I can have the choke on and rev's around the 3000 mark and then it will just die. Once I'm moving the problem seems to happen less but pulling up to the lights and it will occationally die too. This happens more often when the bike is cold but can happen even when I've been ridding around town for an hour or so. Sometimes while slowing down to stop at lights lights etc, I can feel the engine has died and it's only the momentum that is keeping it turning over. A little twist of the throttle and it will bump start again. The other 30% of the time I can hop on the bike and she will start without any choke and will run with out this problem.

Second. Big dead spot between 4000 and 6000 rev's. Twisting the throtle in this range and it's a slow crawl out of it followed by good acceleration afterwards. Twisiting the throtle under this range and there is a slowdown in this range but it is not as noticeable. Opening right up does not sem to make any difference other than faster acceration after the dead spot.

I have been told it could be the neadles, or carb ballancing.

I also have a KN Filter and aftermarket pipes. I do not know if the bike has been retuned for these additions.

Any ideas or offers of help would be gratefully accepted.

[Chookah]

It does sound like carby's
Be methodical and you will find it and resist the temptation to fly off on aftermarket jet kit tangents before checking everything and getting the basics right.
Get armed with a workshop manual.

Pull the carby's off and adjust all the things that can be adjusted back to the original factory settings.
This will probably amount to float levels, pilot screws and maybe (if they are adjustable) needle height setting. The manual will also probably tell you how to set the butterflies as well.
While you are in there remove and blow out all the jets and inspect for things like worn needles, out of round emulsion tubes, worn needle & seats, worn butterfly spindles.

Even if you do find things a bit worn, but find major discrepancies with the adjustables like float levels etc, put it all back together and give it a try anyway. You haven't spent any money yet (except time), so there is nothing to loose.

And don't get too worried about not being able to balance the carby's (you will need a 4 barrel manometer to do it, which you are unlikely you to have). If you have made all the adjustments by the book it will be reasonably close anyway. Get it done later on down the track when the big problems are sorted.

Another important point is that merely by getting in there and having a look you might discover something blatantly stuffed anyway.