Fuel Leaking

[EviLKarL]

Hello all, just joined the forum.

I recently bought this bike for my daughter, however after a few minutes of the fuel tap being turned on, it leaks fuel into the air filter and out the fuel line that comes out of the bottom the the bowl. I have tried cleaning the carb and the seat appears fine, the bike is almost brand new with only a few hours use. Any help greatly appreciated.

 

[my67xr]

welcome to Miniriders,


what carby does the bike run?
sound like some of the plastic bits from inside the petrol tank weren't flushed out before filling it.

sometimes they will travel through the tap, down the hose, into the carby.
if you take the carby off, remove the fuel bowl,
then the pin holding the float, you will need to take the needle and seat out and blow through that inlet tube, to get rid of the foreign object holding the needle and seat open.


if that doesnt work, turn the carby upside down and take a pic of the float in relation to the base of the caby.
it may be set to the wrong float level ?

 

[EviLKarL]

Yea not sure what the carb brand is, the engine is a Lifan.

Edit, it could be a 26mm MOLKT

 

[EviLKarL]

Here is the carb, any comment on the float height?

 

[my67xr]

float height looks normal.

where the brass seat is, for the needle and seat.
can you remove the seat without damaging it ?
i have cleaned out a few carbys that are constantly flooding,
and found either rubber or plastic bits inbetween the seat and the fuel inlet tube.
sometimes blowing through with compreesed air isn't enough to get these bits out.
the seat may need to be removed ?

 

[EviLKarL]

Ok I'll try that thanks my67xr

An update on what i've done, pulled carb apart, cleaned out with compressor, adjusted height of float to several locations to test. Tried the float height according to this thread http://www.thumpertalk.com/topic/538814-now-my-26mm-molkt-is-peeing-gas/.

No luck, Petrol is pissing out the tube on the side of the carb, not the one in the bowl, but the one further up.

 

[EviLKarL]

even when the bike is running it pisses out this tube, then its simply chokes on fuel and dies

 

[my67xr]

do you have a pic of the vent tube where it's coming from ?
can you follow it down and through into the base of the carby ?

when the carby is reassembled, can you hear the float moving ? it is not stuck ?

try having the fuel bowl off and connected to the fuel line, it must be a problem with the needle not sealing off into the seat when the float rises.

 

[EviLKarL]

ok give me a sec

 

[EviLKarL]

Highlighted is where fuel is pissing out, it also pisses out the lower one as well.

 

[EviLKarL]

Don't think I can get the seat out without damage. Floats are moving. I tried without the bowl on and sure enough, fuel flows when bowls are dropped and stops when I raise the float manually.

I raised the float level again, a little higher then the pic here http://www.miniriders.com/attachments/carby-tuning/8477d1374969255-fuel-leaking-img_1466.jpg Seems to have stopped pissing out the tubes now, but still a little coming into the air filter though.

Might just look into buying a 22mm Mikuni carb. Anyone know where i can buy one in Brisbane?

 

[my67xr]

try having the fuel bowl off and connected to the fuel line, it must be a problem with the needle not sealing off into the seat when the float rises.

did you try this ?


sometimes when playing around with the carby, there is a chance you could push on the floats a little.
this can bend that centre tab down and raises the float level, and will cause the fuel bowl to overfill.


i would be bending the little tab in the centre of the 2 floats upwards a bit more to make the needle and seat close earlier, and try it again with the fuel bowl off.
do it over an ice cream container to stop the fuel going everywhere

 

[my67xr]

i also noticed in your pic, the gasket has swelled from being soaked in fuel.
carefully remove it and dry it on a clean cloth, it should shrink back to it's normal size again after 5 or so mins in the sun

 

[my67xr]

have you looked closely at the tip of the needle (from the needle and seat) to check that the viton rubber seal is not damaged in any way?
a magnifying glass helps to see it clearly.
the tinyest piece of plastic or dirt can make them stay open too.

 

[EviLKarL]

Yea I did. The centre tab doesn't bend easily mind you, its pretty solid. As i said, I have adjusted the float height so the bowls are really high out of the carb base, the opposite to the adjustments I've been doing. See my previous post.

 

[my67xr]

yeah i see the floats are set lower,
so are they shutting off the fuel flow now ?
the fuel level in the bowl with the carby all assembled again should be somewhere around 3/4 level when the needle and seat are closed.

to check it you could undo the drain screw at the bottom of the bowl and put some clear tubing on the barb
then hold the tubing up past the top of the carby and turn the fuel on.
the fuel will flow into the tubing and the level shown in the tube will be the same as the level inside the carby.
like this,
the pic is of a Mikuni copy carby, but the same principal
it shows the level is set at 25mm below the base of the carby (mikuni setting)

 

[my67xr]

this pic is also of a Mikuni 22/26mm copy carbys' float
but you are bending the centre tab here upwards ?
it is very easy to bend, being made of .8mm thick stainless steel

 

[EviLKarL]

I'l give it a go with the clear tube and undoing the bowl drain screw. Yes I am bending the correct tab on the float thingy. Thanks for all your help my67xr.

 

[my67xr]

Might just look into buying a 22mm Mikuni carb. Anyone know where i can buy one in Brisbane?

maybe PM rotn50, mick might be able to help you out, or point you in the right direction