Fuel leak from overflow

[snaphappyninja]

hey guys, bit of advice needed.

have just put a new tank on my @, 43l touratech (i know, unecessary but it looks great ) it's got 2 tubes on the underside which i assumed were overflow tubes. i connected both of them using the overflow tube from the existing tank (2 tubes conected by a "Y" piece into 1 tube)
i am now getting a lot of fuel from the overflow, an awful lot more than i would of reasonably expected.
am now thinking that one of the tubes is an air vent. would connecting these together cause the fuel leakage i am getting? any other ideas??

speaking of tubes under the tank...
on the existing @ tank there are 2 vent holes, one large and one small. there is one large tube to connect to the large vent hole and then the tube i mentioned above (two tubes connected to a "Y" piece into one tube) from which 1 one of these obviously connects to the small vent. i can't seem to find where the other one of these 2 tubes connects? any ideas?? more ideas that is???

[YEN_POWELL]

One of the two holes coming out the tank bottom is for letting excess petrol out when you over-fill at the filler cap. When you open the filler cap you can see the opening that it connects to. Chuck some fluid in the top hole and see which it comes out of at the bottom and I would assume that pipe is redundant with your new tank.

[BobA]

43 litre !!!!

Jeeezus, hope you can afford to fill it up at current UK fuel prices.

What do you think the range on that mama will be?

Nice One

Bob

[tedmagnum]

I havnt seen the tank but it should have a breather pipe as well as an overflow pipe.

[snaphappyninja]

ok after further investigation some interesting results.

pipe at front was overflow from the cap as suggested and the rear is a breather/overflow from the tank.

put the tube i was using into a small bottle and tied it to the frame just to see how much petrol i was losing. LOADS a small 35ml bottle was virtually full after a 3 mile ride....imagine that every trip!!!

so now i separated the pipes and put two new overflow pipes on. also put both of these into bottles just to see results. as suspected nothing from overflow and alittle bit from the breather - a lot less than before but still not an insubstantial amount.

now for the confusing bit - the bottle that had the breather hose in it had maybe 10 ml of petrol in it at the end of a ride and i put the bike in the garage. checked it again in the morning and the bottle was empty??? thought "ok the bottle has leaked" - checked the bottle, no leaks. cold night so i don't think it evaporated, so where did it go??? tried this again with same results, i assume somehow it is getting sucked back up into the tank??? anyone got any explanation for all this?

also wondering if anyone else has found out if they are losing any petrol through the breather??? i was always envious of how much tank range others said they get and mine was always pretty shoddy. makes me wonder if this is a problem i've had for a while and just not noticed?? anyone know what causes fuel to come out of the breather???

[snaphappyninja]

PS

Bob,

cost me £35 to fill it up and i reckon it should do around 350 to reserve. looks awesome

Yen,

thanks for the advice mate, worked like a charm and necessary as Touratech were very little help. "sorry mate, we just sell 'em. they come in boxes from Germany and we don't know that much about them"

[YEN_POWELL]

When your engine heats up it's effectively warming your tank and making the fuel vaporise. In fact on my FJ12, after a long run, the petrol cap (they have a pinhole breather in them too) used to whistle like a kettle with the escaping fumes, a good reason for not smoking in a garage. Petrol will evaporate if not in a sealed container even in the cold.