Fuel leak

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   Afternoon all,

I've got some fuel coming out out of the vent pipe that connects to the bottom of the tank and then through to the hole inside the filler cap. 

I first noticed a bit of fuel under the bike after a ride. After a chat with AP I found a leak coming from between the tank and the fuel pump. I heated the tank up, bent it back into shape and put it back together. That stopped that leak but now there is another. To check it wasn't running down the outside of the hose I plugged it and went for a ride. Came back and unplugged the hose and fuel came out. It had also backed all the way up the hose and was coming out the filler cap, only a tiny bit but it was on my jacket. When I opened the filler cap there was a little bit of pressure and fuel sitting around the lip. 

My question is, how is fuel getting to this hose with the cap closed and can it be fixed or does it need a new cap? 

Cheers. 

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martinh Members Profile Send Private Message Find Members Posts Add to Buddy List Moto3 racer Joined: 14 Sep 2015 Location: plymouth Status: Offline Points: 90	Post Options Post Reply Quote martinh Report Post Thanks(0) Quote Reply Topic: Fuel leak Posted: 11 Dec 2015 at 12:39
	Afternoon all, I've got some fuel coming out out of the vent pipe that connects to the bottom of the tank and then through to the hole inside the filler cap. I first noticed a bit of fuel under the bike after a ride. After a chat with AP I found a leak coming from between the tank and the fuel pump. I heated the tank up, bent it back into shape and put it back together. That stopped that leak but now there is another. To check it wasn't running down the outside of the hose I plugged it and went for a ride. Came back and unplugged the hose and fuel came out. It had also backed all the way up the hose and was coming out the filler cap, only a tiny bit but it was on my jacket. When I opened the filler cap there was a little bit of pressure and fuel sitting around the lip. My question is, how is fuel getting to this hose with the cap closed and can it be fixed or does it need a new cap? Cheers.

redratbike Members Profile Send Private Message Find Members Posts Add to Buddy List Moderator Group The Collector Messiah Joined: 07 May 2008 Status: Offline Points: 16331	Post Options Post Reply Quote redratbike Report Post Thanks(0) Quote Reply Posted: 11 Dec 2015 at 12:43
	ok from the fueal cap there is an overflow pipe and also a drain for water/fuel these pipes go back through the tank to either the pump base plate if its a metal tank or the tank itself if a plastic tank. these perish and allow fuel to leak out down them....very common issue with these bike especially the age they are now. its a case of draining the tank,pump out and replacing the hose with sumersible fuel hose so that it doesnt react with the fuela and cause issues. Griff has this in stock along with the correct clamps. allow a couple of hours tops to replace


Rybes Members Profile Send Private Message Find Members Posts Add to Buddy List Premium Member Joined: 07 May 2015 Location: Denmark Status: Offline Points: 1958	Post Options Post Reply Quote Rybes Report Post Thanks(0) Quote Reply Posted: 11 Dec 2015 at 13:18
	im no expert but it sounds as if the tank vent is blocked
	ive just got my first vtwin and i think i got the right one

martinh Members Profile Send Private Message Find Members Posts Add to Buddy List Moto3 racer Joined: 14 Sep 2015 Location: plymouth Status: Offline Points: 90	Post Options Post Reply Quote martinh Report Post Thanks(0) Quote Reply Posted: 11 Dec 2015 at 13:50
	I thought it might have been the pipes that are inside the tank but when I had the pump baseplate off it looks like they are an integral part of the tank. It's a plastic tank on a gen2. I thought the holes around the seat of the fuel cap were for overflow but even with the cap closed, fuel manages to get onto this lip and down through the hose.

martinh Members Profile Send Private Message Find Members Posts Add to Buddy List Moto3 racer Joined: 14 Sep 2015 Location: plymouth Status: Offline Points: 90	Post Options Post Reply Quote martinh Report Post Thanks(0) Quote Reply Posted: 11 Dec 2015 at 13:56
	Also, what sort of impact would a blocked vent cause. I ask because I've just tried blowing through them from the bottom of the bike and both of them appear blocked.

IanG Members Profile Send Private Message Find Members Posts Add to Buddy List Premium Member Joined: 04 Oct 2010 Location: N Wales Status: Offline Points: 10767	Post Options Post Reply Quote IanG Report Post Thanks(0) Quote Reply Posted: 11 Dec 2015 at 16:27
	I'm guessing a blocked vent would cause either a vacuum or pressurize the tank,whichever it won't be good. There seems to be a few people with leaky filler cap seals as well,I'm sure someone was fitting thicker gaskets there a while back.
	www.apworkshops.co.uk www.apriliaforum.co.uk www.apriliaownersclub.co.uk Looking forward to the next track day

martinh Members Profile Send Private Message Find Members Posts Add to Buddy List Moto3 racer Joined: 14 Sep 2015 Location: plymouth Status: Offline Points: 90	Post Options Post Reply Quote martinh Report Post Thanks(0) Quote Reply Posted: 11 Dec 2015 at 16:44
	Right, I've had a bit of a poke around. The fuel is coming out of the line that goes to the water drain. Some of the paint has lifted under the filler cap gasket and I reckon it's getting through that way. I can now blow air through that hose and it comes out the top. The hose for the vent however, nothing seems to get through that either way. I've had the filler cap apart and the little rubber non return valve is working as it should and there is a little bb in there that is free to move. If I take the filler cap off I can blow air through the hose/tank no problem. Is there likely to be some dirt inside a small airway in the cap or something? I don't want any kind of pressure inside the tank causing trouble.