Well, as I sit here writing this, I'm currently awaiting a pick-up van, but ever the impatient one, I thought I'd try and get some proper help asap...
Problem: pootling down borough high street when all of a sudden the engine starts to splutter- put it into neutral and pulled over, tried to start it and the needle jumps rapidly to 2000 then back to almost 0 repeatedly, as soon as I try to give it some throttle the spluttering gets worse, I get serious backfire, a lttle flame from the end can and it dies... It starts ok, but won't idle for long, (spluttering gets worse) and it dies after backfiring. So... Any ideas gents? Obvoiusly your invaluable help is greatly appreciated...
Smoky.

vacuum hose on OK?
deffo got fuel?
reserve on?
turn your lights off and see if it any better.

Dunno about the vacuum hose-
Definately got fuel-
Tried lights off- no difference
Reserve, off, and fuel on- still the same....
I'm hearing an odd noise from the front of the bike though- under the rads- maybe downpipes have come loose? Would that cause this to happen?

tapping noises? grinding noises?

loose pipes are normally a ticking kind of noise and shouldn't stop it running in the way you describe

might be nasty dude...

Sounds like air being sucked in/spat out...
Breakdown guy seems to think it might be over-fueling and flooding....

when it idles are all 4 cylinders firing ?
i only ask because i had a similar fault months ago where i was riding happily down the road,hit a bump and the bike cut out,it turned out to be a faulty earth.

the way yours was running fine then instant fault makes me think of this

get it home and have a look at it,don't rule out what the dude says but,what jetting changes have you done to it ?

To be honest, I'm not sure how many cylinders are firing...
Will check all the earths 2moro-
No changes to jetting- been running fine ever since yamamoto system went on- a little popping from the end can. But the guy who fitted the system said it wasn't super snug anyways...
I have a video of the problem, will post it up as soon as I can....

i only ask about the cylinder as thats what helpped me figure out i had an earthing problem,the front pair didn't earth throw the bracket so didn't fire.

to be honest it's annoying but it'll get sorted with some help from the guys on here.

next time you have the bike started from cold simply check the header pipes and see if they are all hot,this is a good indication to see if all cylinders are firing.

the backfiring is usually a indication of over fueling but would also happen if one cylinder was not firing then maybe firing.....being a bit temperamental!!!!!!

i had a similar problem of late,where there was a funny noise from the front,directly under the front of the engine and cylinder number 2 was stone cold......but now all of a sudden number 2 is heating up again but the noise is still there.

i believe the noise is the exhaust rattling a bit...........or i hope its this



william

Will definately check the pipes and earths tomorrow- have a funny feeling it could be the carbs- as the guy who serviced it told me they were absolutely filthy- but he never said anything about replacing the gaskets or seals or anything....
Maybe just a case of carb trouble?(Fingers crossed)