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erixtar1992

bike carbs pissing fuel out of overflows

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erixtar1992

yo.. right..

put cbr600 bike carbs on my mk2, i have checked all jets and they are clear and float bowls seem to be sealing fine when i checked them.

now, the car will start up and rev happily when the float bowls are NOT completely full of fuel

but when they fill up, the car will bog down, and fuel will start pissing out of the breather pipe on the top. if i hold my finger over the pipe then fuel will come out of the brass tubes next to the trumpets.

i am fuelling it using the standard mk2 mechanical fuel pump, and a y piece with the carbs + return on the y and the fuel inlet pipe on the straight part.

i can blow down the return line but i have to blow quite hard.

ideas?

Edited by erixtar1992

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Cymro

too much pressure.

i know your using the t-piece so there might be a kink or blackage in the return hose.

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erixtar1992

like, i can blow down it not too hard, but if i try and blow harder it wont have it lol

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erixtar1992

think it may be the return causing the problem

i put the return pipe into a fuel can and it stopped the problem... nalf filled up quick though haha.

sourcing the blockage is gonna be a pain though..

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Cymro

check your FB. :lol:

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erixtar1992

bit dark to do it now :/

pissed off as i needed the car to drive to work tomorrow. gonna have to get the train now which is long!

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Cymro

I'm still suspect of your swirl pot being the cause. Ill smash open the broken one i have here tomorrow and see what the valve thing inside actually does.

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erixtar1992

yah but when usiing t piece it does it too

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harris.racing

So it runs better with return into a pot?

Too much pressure or float heights, did you bother taking the floats out and checking how clean the taper is on the float needles?

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erixtar1992

checked the taper, was spotless on all four.

yeah it ran fine with the return straight into a fuel can which makes me think too much pressure is building up

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harris.racing

Hmmmm you need that return freer flowing!

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erixtar1992

yep. the return is stopping me driving to work tomorrow :(

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Cymro

what ID is the return?

I'm still thinking there might be a kinked line somewhere, even the slightest kink will raise the back pressure.

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erixtar1992
what ID is the return?

I'm still thinking there might be a kinked line somewhere, even the slightest kink will raise the back pressure.

6mm i think.

yeahh its just finding it that will be the problem lol

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Cymro

6mm is huge. :lol:

Have a look where it goes under the car from the engine bay, mine used to try and kink there.

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erixtar1992

both my inlet and return are 6mm on this, on my later mk2 they were 8mm.

just had a look under the car with a light and couldnt see anything abnormal :(

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harris.racing

I couldnt even blow down the return on my 6n, strange.

Hmm thinking

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erixtar1992

wierdd.

do you agree that it sound like its fuel pressure related?

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Cymro
I couldnt even blow down the return on my 6n, strange.

Hmm thinking

Bigger Lungs? :lol: :lol: :lol: :lol:

I'm a brass player so its no problem for me. :lol: (very careful wording there) :nod:

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harris.racing

Meh lol.

I'm thinking Eric, I'll prob phone you about 4am when I have a sudden realisation

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erixtar1992

SHE LIVES!

i swapped the fuel pipes around and somehow its fixed the problem LOL

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Cymro

Strange. :lol:

where were they wrong?

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harris.racing

I did consider that but assumed you'd have checked lol

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Cymro

i told him to check the swirl pot as well.

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erixtar1992
Strange. :lol:

where were they wrong?

no i mean i swapped the fuel inlet pipe to the pump for the return pipe :lol:

for some reason its sorted it? return pipe must have been causing a little too much back pressure?

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