It's not the 3TJ engine, it's the 2TK .... the FZR400R SP, it has a close ratio box which is why it needs revs to pull away on a hill.

It's a wierd on though.
Have a look at the side stand, check if there are 2 return springs that the smaller one isn't broken, this could move the sidestand and stop the engine.

If it was fuel starvation the revs would rise before cutting out and as said it would take longer than a couple of seconds. Float heights would be fairly constant due to the fuel pump.
But it's when you stop ... like Will says there are 4 things that are happening here
The forks compress - can't think of anything there
The brakes are on - electrical draw or faulty switch, unplug the brake light switch and try it.
The clutch pulls in - same as the brake switch.
The bike dives - you'll need to check all the block connectors, make sure the loom isn't moving and pulling them apart. Alarm ??? faulty movement detector ???
I take it the ignition lights stay on.

Right then.......proper engine anyhow.....
Mikuni BDST32 Carbs.(from the 2TK supplement)

Where are you getting your float height info from ?
But more to the point.... What have you it set at ?

Must admit mind,I have only ever cleaned mine....never needed owt else.

Boris; As for the fuel height.....
I am thinking if its too high to start with, the engine is just able to burn it but if if it is sloshed forward at idle it is swamping the cylinders.?

LKey; What happens if you make the front end dive with just a little throttle on ?

Isn't there a venturi system for the idle ... ??? So wouldn't that be the mixture screws at the front of the carb ???
All I remember is what I learnt at college

We perhaps need a little more info from the owner before more conjecture,mileage and such ?

Supposition=
If high mileage and emulsion tubes/needles are worn; main jets will not seal and high fuel level would swamp engine with insufficient airflow ?
Is vacuum at idle is high enough to pull excess fuel through badly worn main jets or incorrect needle settings if fuel level is temporarily overhigh ?
Would the effects of the above be less significant on a cold engine with choke applied as opposed to one up to temperature ?

Anyone .....?

Perhaps the owner may warm it up and apply the choke without dipping the front end and post up the results.?

Can't just tell him lots of things to do / try like usual

Check the neutral-light @ side stand switch connectors are secure and not earthing out anywhere they shouldn't?

Chris

Change the spark plugs, me fzr used to do this, every time you pulled upto lights unles you keep the engine revving loads, mine had some crap twin electrode plugs, just flooded everytime. Changed the plugs back to standard ngk and its been spot on since.
Try putting the tickover upto 2500rpm see wat happens.
Just a thought.
Cheers
Ian

Thanks to all for all the information
I can rule out some of the suggestions
I compressed the front end without using the brake - same result
There isn't any alarm system on the bike
The bike does not have a side stand switch
Bike has 12000 km on the clock
We dismantled the carbs completely, cleaned them manually, threw them in the ultrasonic cleaner. Everything looked fine

I will be away over the weekend but try more things on Monday, will keep you posted
Thanks again
LKey

Had the same problem with my 1WG. Your float height is too high. Fuel is killing the engine when it sloshes forward and floods the engine.
Float height of around 12mm from the float bowl gasket surface should sort you out.

Did the crazy Italians put an ignition cut off switch on this bike?
If so is it the right way around?
Have to admit it sounds like its flooding. Try running the bike with the pump disconnect so it drains some fuel from the float bowls then try the front brake test again, if it helps then it could be too much fuel in the carbs.