Fuel leaking from petrol tap

[Bjorn2ride]

Hey all,
I have a 1990 CBR250RR with a bit of a prob........
it leaks gas out of the breather nipple(I think) at the top of the fuel tap located under the gas tank.
Been doing this for a while now so I thought I might try for some insight here. Recently I changed the fuel tap when I first noticed it happening, the rough starting got fixed but stil leaks gas going or otherwise. I think it may be a blockage somewhere affecting some sort of pressure build-up, but not to sure.

Any help with this would be of great help.

[quickbuck]

Welcome to Kiwibiker.

Sounds to me like you actually have an internal leak in your tap.

The other "Breather nipple" i think you are referring to is actually a Vacuum tube, that opens a valve when the engine is going.
This is to prevent fuel coming out of your tank when the engine is not going.....

Can't remember the CBR250's fuel tap set-up 100%, but from what you have described, I would say that's what it is.

Only fix is to get another tap...
The Nipple is supposed to be connected by a rubber hose to the intake of the engine somewhere... This is how it gets the vacuum.....

Now, remember the rubber inside these is 20 years old, so many will be getting a little tired..... AND Ethanol loves to eat rubber..... So don't put Mobil or Gull Hi-Octane in it....

hope this helps a little.

Oh, and I know you are new, but for serious answers in the future, post in the Mechanical Section....
Also, if you have a camera, take some pics and post them up... I might be a little off track.

Let us know how you get on.

[motorbyclist]

replace or repair this tap ASAP... or take out fire insurance; your call.

Assuming the tap is similar to the 400cc hondas of the same period, that nipple either a breather or is as above a vacuum tube to stop fuel leaving the tap while the engine is stopped, to try stop spillage and/or fire if the fuel line breaks or comes off.
This vacuum operates a diaphragm which pushes against a spring to allow fuel to pass. Over the years a previous owner may had decided this was too restrictive and as per the HRC manual or what his mates told him in the pub, fiddled with it so it didn't need a vacuum line.
Either way, over 20 years, it may have perished or been dissolved by ethanol or other solvents. You can buy kits to replace this or just replace the tap from one a wrecker has - I suggest calling http://www.econohonda.co.nz/

[Bjorn2ride]

Thanks for your input, I realise it has a vacuum hose on it which I replaced when I got the Fuel tap. Also replaced the main feed line into the engine. The vacuum line comes out the side with breather nipple on top towards the tank. The replacement was a second hand one from a wreckers as a new honda version is $350 plus. I was hoping for a cost effective alternative.

In the future I will post any such queries on the mechanical section.

thanks

[Icemaestro]

I had the same problem on my 92 cbr for about 6 months (till i finally got it fixed) so you probably don't have to worry about it catching on fire...I did some 2h rides on it without any probs.. This is a very common problem with the cbr250rrs, so good condition fuel taps are hard to come by. George the MC doctor eventually found a replacement piece to replace the half of it that the diaphragm is contained in (the side with the breather nipple to connect with the vacuum). I believe he got this from another model honda bike from the same era, so ask around I guess, maybe try email him? (do a google search..george the MC doctor, auckland).

[Bjorn2ride]

Hey all,

The prob I have with my little CBR250RR 1990 is whether it is off running or sitting I have fuel leaking out of the breather nipple on top of the fuel tap. I have recently replaced the fuel tap but the problem is still there.

The replacement part was off a wrecker so maybe I just swapped one prob for another.

A new fuel tap from Honda if they can get one would set me back $350 plus.

Any other ideas as what may cause this prob. I realise there is a vacuum hose conected aswell to the tap, thimking maybe a blockage somewhere in the works.

P.S I hate having to pay bike mechanics to do jobs that should be simple.

[Bjorn2ride]

Thanks for your input

I will look him up.
CHEERS

[Bjorn2ride]

Hey shot replaced with new parts from Honda and seems sweet now. The part with the diaphragm was the bad girl. swapped out for all new bitz.

VERY NICE

[Icemaestro]

"new parts"? You went for the ex japan new part?how much did that cost???!!

[Bjorn2ride]

I bit the bullet and spoke to the guys at Botany Honda.

The fault was with the diaphragm in it. Because of all the crap in my fuel it perished the Diaphragm. Replacement bits n bobs only cost $45 from said store. About 45 mins of my personal labour to fit and I was away laughing.

Cheers for all the help those that replied
Massive thanks to the lads at Botany Honda

[Icemaestro]

That's good, george told me he couldn't get the diaphragm by itself, hence having to get the half side of it...I paid about 40$ too so good job:-). The diaphragms perish anyway, not necessarily due to your fuel - the cbr250rr has an in-tank fuel filter to filter out crap...

[motorbyclist]

we're talking chemical crap - ethanol isn't the only chemical that might affect that rubber

[Icemaestro]

Oh true, what other kind of crap is there in your standard 91? Just out of interest?

[motorbyclist]

Oh true, what other kind of crap is there in your standard 91? Just out of interest?

depends on the supplier as they all put in different additives for cleaner burning / octane boost etc etc - might be worthwhile doing a search on KB/google for that info

oh, and have you tried running your bike on 98 for a while? you'd be surprised at the improvement it can make to the smaller bikes and often it even works out cheaper per kilometre

[Icemaestro]

hmm...okay...now I definately know no gains can be made from running a stock mc22 on 98...it can even impair performance. I know cause I accidentally put 96 in mine...created a flat spot between 10 and 11000rpm