Fuel pouring out from carb outflow hose, engine running badly.

[noggythenog]

So I ride about 120 miles up to glencoe and the bike is fine and gets a good blast, I top up the tank for return journey, mpg is fine, on way back we pull in for a quick break and I smell petrol then notice fuel pouring out from the hoses underneath the bike, bike runs but gets progressively worse and vibration felt through pegs with dash sometimes vibrating also,example overtaking in 3rd is a lull, then picks up until mid rev range lull again before apparently then going full power at high revs like a v-tec kicking in on my old type-r Honda car, so I get home eventually by skin of my teeth and use a full tank of fuel in 100 miles, half generously donated to the ozone,the carb floats and seals have already been replaced by Yamaha after it did similar in my dads garage, I wonder if anyone has suffered the same, could it be the floats again or could it be simply a bit of dirt got in from the tank etc, it's not like it happened straight after sitting in garage for a while as it ran fine all the way up and it got a good thrashing.its in the garage again so I'll see what they come up with and post result.

[Fazerider]

If the carb floats, valves and valve seats have already been replaced for this problem it may be that the problem is elsewhere. The fuel pump is supposed to cut off when the back pressure reaches a certain level, if the pressure switch has failed perhaps the pump can continue to force petrol into the carbs despite the resistance of the float valves.
Just a theory. I've no idea what the normal cut-off pressure is... and measuring it will require either specialist equipment or some ingenuity.
It'll be interesting to hear what your garage says.

[noggythenog]

Thanks for the ideas Fazerider, being a silly boy i posted this on the fz6 forum by mistake so its on both forums now,

for info though to follow is pasted in giving the latest update and ill let yous know when up and running good:-

Alas they think they've solved it, mechanic asked me to go down take a look,found some tiny particles of metal that have been bouncing about,looks like they've come from imperfections with the casting marks on top face of one of the carbs,one of the pieces suspiciously had taken the shape of the hole that the needle goes into as if it had been sucked in and blocked it,they gonna rebuild the bike and see what happens, the mechanic wasn't saying it as if it was anything he had often seen, bit of a strange one indeed.fingers crossed.