Appreciate the feedback so far!

I guess my main question is what am I missing with vacuum? I mean, I now understand vacuum better, more vacuum means more air/fuel pulled through, hence why the lack of vacuum would cause a stutter (some things take time to sink in!)

So,

No obvious fuel issue from the tank as breather hose blows through and there’s no gasp as you open the tank. I ran the engine with the fuel valve closed to drain the filter/pump and watch the pump fill up again and it did so pretty proficiently!

The air box is clear without obstruction and the new (white plastic, metal grilled paper finned) filter has done maybe 150 miles.

I tried the pilot screws down to 1 turn though they seemed to toughen the idle so I’ve turn the pilot screws to 3 turns out which seemed smoother, and then loosened the idle screw off to get the idle back to 1150-1250 rpm, then checked the balance and the TPS. TPS is at 5000.

I then ran the engine and sprayed engine start and WD40 around all the seals/connectors to see there was any surge in power/leaks allowing the spray to get in, and there was no obvious difference (just the constant little surge in revs off idle that happens which can also be seen in the video below) I did this also when I refitted the cleaned out carbs, as had seen that on the forum here

The Balance and throttle response is as below in attached video.

After rebalance and increasing pilot screw turns, I did go for a little ride, and there is some improvement to the low Rev stutter, but still evident. 

I have still to check float bowl levels, but finding a plastic flexi tube has been a bit of a challenge today!

Is there anything blatantly obvious/simple I’m missing to create more vacuum? Does a video of the engine running give anything away?

Again, many thanks for your time and responses.

Hi Fellow Foc-ers! (Is that alright to say?!)

So I have been using your info for the past few week helping me rebuild a 2001 FZS600 that had been off the road for 5 years.

It’s been a fantastic learning curve so far, but now I’m struggling…

It doesn’t like being in a low rpm and pulling away.

1st gear pulls away okay and the engine seems happy,
2nd gear, below 3,500rpm it judders quite viciously,
3rd, 4th, 5th, 6th, it bogs down below 5000rpm.

It would likely judder in the higher gears at a lower rpm, but I wouldn’t be in them at any low speed.

It doesn’t Idle without the idle adjust screw/butterflies opened a bit, but even then at 1250rpm it surges every couple of seconds.
Pilot adjust screws are set at 2 turns, though have tried at 1.5 turns and 2.5 turns which don’t make too much difference to idle speed.

Above 5000rpm the engine really sings now, and pulls constantly well especially after the work I’ve done below (previously it even bogged down at 7-8000 rpm), but none of the jobs have rectified the low speed rpm judder.

The clutch does seem to make a chatter on idle.
 
It does smell like a rich mix on idle, I.e too much fuel?

Soooo,

Following reason other people’s advise on here,

I have stripped the carbs,
cleaned/rebuilt/balanced/jets cleared/all pipes flushed. (Balanced visually when carbs removed and with a 4way vacuum gauge)
New orings fitted on main jet and float needle and float needle valve (remembered the 4 little screws hold the valves)
Fitted new air filter (though not k&n)
Fitted new iridium spark plugs even though originals were brown and gapped well.
Replaced cracked carb/engine rubbers
Emptied as flushed fuel tank.
Checked caps for sparking and they do all spark well or at least sound like they do, and don’t arc in the dark.

I have a new fuel pump (not yet fitted) as I thought it was fuel supply when it bogged down under high rpm.

What have I missed? Fuel/air mix? Float level? Clutch issues?

Any help would be greatly appreciated as the bike is fab, just not round town and don’t wanna have people look down on the Fazer as I rev the nuts off it and feather the clutch at 25mph through town trying to stop the judder!

Many thanks!!