Fuel spilling out of tank

In have just bought an GPZ 100RX

 Took it out for a ride today after i filled it up and stopped and fuel is leaking out the filler, not the bit of the fuel cap than opens but the bolt bits of the fuel cap.

It literally pours out.

I took some petrol out thinking i may have over filled it but i took half the tank out and still doing it.

 The breather bipe at the end of the tank seems blocked, i took it off the tank and is clear but when on the tank its blocked.

Is this the pressure blowing the petrol out because the breather is blocked?

any advice on clearing it? or what it maybe?

many thanks

Kev

Cor. That's a new one. No idea but to start with:

Does it do it with the engine running? Or all the time? If it's only with the engine running then something maybe pressuring the tank / breather pipe.

Does it do it with the tank cap open? If so, then at least you know it's not pressure in the tank.

Does it do it even with the bike upright? Or just leaning over on the side stand? Do you think the fuel level in the tank is well below the bolts? i.e. are you sure it's being forced out, or is it just gravity? Fuel does "whick" very easily.

Normally the fuel tank "breather" pipe is a drain that runs from the area around the filler cap, to just below the swing-arm - the idea is it catches any leaks and stops them running over the tank. If you've got fuel being forced from the area around the filler cap (thru' the bolt holes?) then I'd guess the other end of the breather has been connected to part of the fuel circuit on the pump side. But I didn't think those bikes even had fuel pumps! I take it you mean a GPZ1000RX?

Any chance of some pictures?

thanks for the replies,

I ran the bike 4-5 miles put the bike on the side stand and 5 mins lates petrol started leaking out of the cap mounting.... it was pretty full so just put it down to that.

I drained half the tank and and closed the petrol cap...five mins later was doing it again. I rode the bike 2 miles and petrol was p*ssing out of the cap mounting.... but when i opened the cap it stopped... i even took the tank off and it was still doing it. I have tightend the cap allan bolts as much as poss but still doing it.

I think it definately pressure.

 if i opened the petrol cap and blew up the breather pipe should I be able to blow up the pipe?

Dont think it has a fuel pump.. but will strip it down and take a look

yes its the gpz1000rx...old school

Well if it's doing it without the engine running then it seems unlikely to be a fuel pump problem - and as you say, it shouldn't have one fitted.

If it's like all my previous bikes (MZ excepted) then I'm pretty sure that the "breather" pipe is NOT actually a breather pipe. The tank usually breathes thru' a tiny hole in the filler cap.

Instead, the pipe should be merely an "over-flow" drain pipe - any fuel spillage (or rain water) collecting in the step-down area around the filler neck should dissappear down a small hole. This small hole is connected via a pipe INSIDE the tank, to where it exits at the rear, underneath the tank, for the connection to the rubber hose which dumps the spillage over your rear tyre.

So, I think that you *should* be able to blow up the rubber hose, and the air come out thru this hole near the filler neck, regardless of whether the filler cap is open or closed. The fact that you can't suggests there's a blockage / damage to the internal metal pipe.

Even if the tank is pressurising (which seems likely since the problem stops with the cap open), this shouldn't be able to force fuel out that's BELOW the level of the filler cap screws - it would simply force air out instead. If the fuel was bubbling and foaming to a silly extent then I guess maybe it could - can you see the fuel? Is it foaming like a hot tub?

BUT, if the internal over-flow pipe was ruptured below the level of the fuel, then any pressure build up in the tank could then force fuel up the pipe until it came out in the area around the filler cap. Normally it would just allow fuel to drain out of the rubber hose all over your back tyre, but if the internal pipe is blocked then that couldn't happen.

I'd be inclined to unbolt the filler cap allen screws, and temporarily "cork" the filler neck (need to make a good seal). This way you should see where the fuel is actually coming from.

Still not sure how the tank would be pressurising. Possibly a chemical reaction to something in the tank?

When the fuel comes out its not bubbling out its like its coming out in waves if that makes sense.

I opened the tank cap and the next was filled with petrol including all theholes... i dried to up with kitchen roll and closed it 2 mins later i opened it again and it was soaking.... But i'm the same as you not sure how much presure it would take to drag the petrol up from half the tank down... unuless its sucking it from somewhere else.

Also ran the bike again to check and was fine untill pressure built up then you could actually hear the tank gurggling.

If the pipes are blocked... how best to un block it.... I tried to push a copper pipe up the breather pipe but has a bend in it that i cant get it round.

If the fuel level was at or above the filler cap then it wouldn't take much pressure at all to get it to leak out. But, if the fuel level is BELOW the cap then it would take an infinite amount of pressure (or a LOT of bubbling) to get fuel to come out of the tank. UNLESS, it's being pressure-pushed thru' a hole in that internal pipe, and from there it's unable to go down the rubber hose so is coming out around the filler cap. I reckon that metal pipe is both blocked (from the rubber hose) and punctured (to the main tank).

Still don't know what would be causing the pressure tho'.

What hoses are connected to the tank?

Overflow hose should be left open at the non-tank end - I assume this is so?

Should probably have a main fuel cock on the tank with two hoses that run down to the vacuum operated fuel tap? Possibly via a vacuum operated fuel pump?

If there is a vacuum tap or pump, try bypassing them temporarily to let the petrol straight to the carb. If one of the inlet valves is leaking then I guess this could back-pressure the inlet manifold, then the tap, then the tank. Would require several perished seals tho' and again - very far fetched!

Any other hoses connected to the tank?

Given the fuel coming out the top of the tank I'd be very nervous about trying to unblock the metal pipe. I reckon you'll just end up with a permanent fuel leak out of the tank, down the overflow pipe. 

Sorry - without seeing the bike's fuel system I'm clutching at straws a bit.