stuttering fzs 600

[Gnasher]

good to see ya still at it mate   i found a video on me camcorder i made a couple of weeks back to post on here but never got round to it. take a peek and see what you think. her bike is no more so this doesn`t really apply anymore but maybe it could ring a bell with others ! good luck with your spanner man
motorcycle fuel pump problem=

Matey your diving too deep me thinks 

The electrics on the Fazer are pretty much bullet proof if the fail they just stop working, I've never known a Fazer pick coil to cause this issue, if fact I've only known them to fail after crash impact.

I'm 99% certain your problem is fuel/air it is either a blocked or partially blocked jet/s worn jets and or metering needles, damaged float/s, partially jammed open starter plunger.  Strip and check everything again take your time check each jet with a magnifying glass there must be NO damage/scoring on ANY of them pay particular attention to the emulsion tubes and make sure all the jet are the correct jets i.e. size!  The check all the bleed jets/cannels within the carb body recheck the diaphragms the whole surface they often hole right on the edge where they are clamped by the cap, the whole only being expose on large throttle openings i.e. giving it a handful.  Check all the the needles are set to the same and correct height and have all the washers and ring.

I know you've done a lot of work here matey I'm not being funny but you've missed something, remember the needle jet! 

The other thing to check is the rubber caps on the synchronizing tubes make sure they are not split I once had this on a bike that came in doing just what yours is doing!  If you have a Scott oiler check the elbow they don't last more than a few years.  Also check every gasket and seal make sure the carbs are seated fully and squarely in the intake rubbers misfires at large throttle openings are often down to weak mixture and air leaks.  Lastly check the exhaust headers are fully seated and sealed after that mate there is not a lot else you can do other than change all the ignition system and try another working set of carbs.

Thinking about it why not see if you can borrow a set of carbs that you know work straight swap if the problem goes it's your carbs and one of the thing stated above, if it's still there it's an ignition issue which is possible.

It's very unlikely to be a fuel supply problem if you've only got a flat spot/misfire the float bowls hold enough fuel to last a while even on full throttle openings.