Fuel tap /fuel tank plumbing

streetf2 · Post by **streetf2** » Sun Jun 17, 2007 5:26 pm

Can anyone tell me what should go on the small thing on the back of the fuel tap not the vacume pipe as i have this connected,but my bike has a small peice of pipe with a screw in it to blank off the rear connector.I am sure this is not standard.Also on the fuel tank there are two what looks like breathers underneath one small dia one slightly larger.These have no pipes attached and i am sure this aint right .Have looked in haines man but it isnt anyhelp.

Kitch · Post by **Kitch** » Sun Jun 17, 2007 5:51 pm

Having just fitted a new tank:

The fuel tap has 3 hoses: 1 fuel in 1 fuel out (large, each side) 1 vaccuum (small on the back)

The other 1 (larger, tank bottom) is fuel overflow. Look in the filler cap place and theres a hole, this leads to the "rail" looking thing you can see in the top of the tank and overflows overfilled fuel to the nozzle underneath. It needs a hose on so it doesn't gush petrol onto your hot engine.

The other one (tank bottom) is the air breather to stop the tank vaccuuming.

So, your mystery pipe is well, a mystery and doesn't have a purpose I can think of.

streetf2 · Post by **streetf2** » Sun Jun 17, 2007 6:04 pm

cheers for that i def have four on my tap two large petrol feeds one vacume that is horizontal and just behind left fuel feed and a rear down facing that leeks petrol slowly if not blanked off.And i aint got a clue what it is.Can you tell me if i get some pipe for the tank over flow and breather should i just route them down underneath the bike somewhere safe.

Post by **sirch345** » Sun Jun 17, 2007 7:03 pm

The bit you are talking about (that faces towards the ground) is it not a drain from the diaphragm

if it is and petrol's coming out from there your diaphragm needs replacing

streetf2 · Post by **streetf2** » Sun Jun 17, 2007 7:59 pm

sounds good to me but if it is should it not have a long open ended pipe atached rather than a short pipe with a screw in it.Or could this have been put in it to stop the leek and sell it to me.

Post by **sirch345** » Sun Jun 17, 2007 8:42 pm

streetf2 wrote:sounds good to me but if it is should it not have a long open ended pipe atached rather than a short pipe with a screw in it.Or could this have been put in it to stop the leek and sell it to me.

If it's the outlet that I think you're referring too, it doesn't have a pipe attached to it as far as I know

So it sounds like your idea about the pipe with a screw in it could have definitely been put there to stop the leak

The outlet I think you mean is this one below arrowed

(sorry the pic isn't very good, but it's the only one I could find quickly)

streetf2 · Post by **streetf2** » Mon Jun 18, 2007 5:50 pm

Yes thats the one thanks for that i take it it is supposed to be open with no pipe on then because nothing should come through there except air when diaprham moves in and out.In which case i think i have found my slight fueling or misfire problem at 6000 rpm.i did check the diapram when bike was dismantled and couldnt see any holes but i must have missed it.Thanks again.Now i know this must sound painfully clear to those with a brain ,but please bear in mind my bike was lacking these items before i started,but the fuel over fill pipe and breather pipe on the tank! If i understand the incredibly easy to understand idiot proof haynes manual they both connect to the air box top right picture page 4.4 or am i being an idiot.Is that really a good idea for an overfill pipe to run straight into air box.

Post by **sirch345** » Tue Jun 19, 2007 10:40 am

streetf2 wrote: i take it it is supposed to be open with no pipe on then because nothing should come through there except air when diaprham moves in and out.

That's exactly what I would have said

streetf2 wrote:Now i know this must sound painfully clear to those with a brain ,but please bear in mind my bike was lacking these items before i started,but the fuel over fill pipe and breather pipe on the tank! If i understand the incredibly easy to understand idiot proof haynes manual they both connect to the air box top right picture page 4.4 or am i being an idiot.Is that really a good idea for an overfill pipe to run straight into air box.

Looking at the pic in the Haynes manual

The only pipes on my bike (UK model) that attach to the bottom of the airbox are iirc a total of four:-

Two pipes from the cam covers (one from the front and one from the rear)

Two pipes from the carbs (one from each carb) these pipes are quite short (guessing about 30mm long)

HTH,

Chris.

streetf2 · Post by **streetf2** » Tue Jun 19, 2007 8:22 pm

yep thats how mine is going to stay just those four and going to run the others somewhere safe.Thanks again for the help will have to let you know if my faulty fuel tap cures my ocasional misfire problem which i think it might.

Post by **sirch345** » Wed Jun 20, 2007 7:54 pm

streetf2 wrote:yep thats how mine is going to stay just those four and going to run the others somewhere safe.Thanks again for the help will have to let you know if my faulty fuel tap cures my ocasional misfire problem which i think it might.

Breather pipes and drain pipes usually run down and exit just below the bottom of the sump, on a standard bike they are held there by being tucked in behind the left-hand (gear change) side of the little bellypan

I for one will be interested to hear if your misfire does disappear once you've fitted the new diaphragm, it definitely sounds feasible

Chris.