brains trust

[coxy]

ok here's a little problem yesterday I was riding around to a friends new house as I was trying to find it the gtr lost power like it was fuel staved .I gave it a bit of throttle and it cleared .the thing is it spat dirty fuel  out of the fuel tap itself and splattered over the left casing this is the second time its done this .there is a small weep at the bung .and the first time it happened I cleaned the tap and tank there was no dirty brown fuel .why would it do this the lines are clean the carbs are clean.

[slawsonb]

Having trouble visualizing this one, coxy. Do you know where on the fuel tap the dirty stuff came from? (I'll admit nothing jumps immediately to mind, but getting the discussion going... Definitely a quandry...) 
...bert

[coxy]

I would say that the fuel spurts out of the weep I don't know why there would be that much pressure and don't know why it would be dirty

[hardy]

Possibly, there was a vacuum in the tank causing it to suck and back flow through the carb??

Check the tank cap breather is working...?

No other thoughts. A random question/happening tho.

[Mopar392]

Have you made sure, with air, that the fuel cap vent isn't plugged, same symptom's happened to me, sure enough, plugged vent...Lee

[coxy]

Thanks I will.look at that though its really only about a year old nos

[BS Mechanic]

Coxy,

Not sure if I completely understand what's happening, but here are some thoughts:
if it looks like the tap is leaking fuel, check the threaded part of the tank that the tap screws to very carefully for leaks. This connection can develop internal cracks and since the threaded collar which is part of the tap is so close, fuel can run down the tap making it look like it is leaking.  Try using a clean dry cloth to find exactly where the fuel is coming from. Can be tank connection, seal between tap and tank, tap lever seal, or filter bowl seal.

Not sure how this would be related to the fuel starving, that sounds like it might be a separate problem.

Good luck, these can be hard to find!

[slawsonb]

My vote's with the cap vent.
...bert

[ziggy stardust]

Was your bike in strong sunlight at the time Coxy?

Expansion and a blocked vent hole seem favorite, me thinks.

Z

[coxy]

ok there is a weep at the bung which is very minor only enough to have a slight smear of gas on the top of the fuel tap nut ,I don't think I have had a bs that hasn't had a leak there  .on reflection the day was cold though the motor was hot and on both occasions I had just filled the gas tank and when I parked on the side stand a bit of fuel came out from under the fuel cap so it is probably the vent .this does not explain the colour of the fuel which spat out .I will change tanks and fuel tap as well as look at the vent on the weekend .cheers