Started the bike this evening and it was ticking over ok, got it off the choke and everything was normal, then 20 yards down the road it just kind of spluttered and died.

Knowing that the plugs are past their best, I had a spare set with me, so changed them over (cue sounds of a grown man weeping, clutching his bleeding knuckles).

Went to start it again, and it wouldnt fire on any cyclinders at all. Fresh fuel in the tank, and its used daily without any problems.

After full choke, no throttle for 30 secs I pulled one rear plug and there was not a whiff of fuel on it at all.

Any ideas would be appreciated, as its sitting on a roundabout in Guildford for the evening...

is the vac hose connected and in good condition? could there be a fault with the tap ?, turn it to res maybe

Vac hose is connected, though not sure about the condition. Tried res, didnt seem to make a difference. I'm on hols now for a week, so will try to get it home tomorrow then its time to start pulling it to bits again.

Vac hose on the right spigot? The outer one?

not left it a while and got shit in your fuel filter?

nope, vaccuum hose on the correct bit, and its used daily. I'm hoping its the vaccuum hose getting old and tired, as its either a fuel starvation issue or something to do with the ignition.

Does fuel flow from the tap when a vacuum is applied to the tap, may be a dud diaphragm.

aha, thats the sort of thinking i am looking for, didnt think of that! I'll take a gander tomorrow and see what happens :)

If all 4 cylinders are dead, check for spark on a rear plug [easier to get at]
That will prove ignition or not for now.
Look at the vacuum hose where it fits onto the spigot in the rear RHS head, often they perish and crack or break near the sharp bend.
With fuel hose off, tap to ON, vacuum hose connected, spin starter for a second [with kill switch off] petrol should spurt out of tap outlet.

If ignition is faulty then,

1 cylinder suspect plug/cap/lead/ HT connexion.
2 cylinders [front or rear pair] then coil, LT connexion, pulse generator pick up.
4 cylinders CDI, or connectors to it.

Ignore rectifier if engine spins over quickly.

Yup, checked rear plug for sparks and it was fine. Vacuum hose is connected to the tap, so might be worn/perished farther down perhaps. Waiting for the gf to pic me up so I can take another look at the bike and see whats occuring.

Thanks for the help guys, I really appreciate it!

Problem solved, I went back to swap the vaccuum hose and its been nicked