Fuel problems

[Iainhugh]

I've recently done the jets on my ft. Then It was leaking fuel so I replaced the float valve and now when I switch bike off, if  the petrol tap on it leaks fuel from overflow after a few minutes. I have already done away with the original vacuumed petrol tap. Any ideas ?? It's get mot'd in the morning. As long I turn it off its all good but I'll forget
Iain
Scottish highlands

[J6G1Z]

Is it possible that the float is stuck & not closing the needle valve?

J.

[Iainhugh]

I've no idea. It was leaking first time round even when the bike was running. I then changed the needle valve and it leaks few mins after  I kill the engine . If the float was stuck surely it wouldn't run?? There was a diafram in the carb separate casing and near float bowl ,,when I was cleaning it all out.  Is this anything to do with shutting fuel off in the carb
Iain
Scottish highlands

[thumb]

Is the needle valve sat between the 2 plastic pins on the float, had a similar problem when I cleaned the carb and did the jets on mine

[Iainhugh]

The only thing I can do is take the carb back off for another look , although when I put in the new needle valve it did overflow so I've already had the carb off to look inside again. What is the story with the diafram. If you look at bottom of carb it's in a all casing next to float bowl. It's about 15 -20 mm in size with 3 small screws holding it in place. The diafram has a plunger / pin kinda thing on the top going up into carb and a spring on the bottom side of it. When I cleaned out carb it didn't look too healthy in there.  But for now I'm just gonna have to switch off fuel straight away,
Iain
Scottish highlands

[wrk2ride_ride2wrk]

try giving the bottom of the carb a sharp couple of taps while its leaking, if it stops, its likely the floats are sticking and the needles not seating

[triguyracer]

This is most likley not the problem and a long shot but see if you have a leak in the float itself this can cause the float to stick by having fuel in it and not raising up far enough to put enough pressure on the pin to seal it.check by putting in a small cup of fuel and holding down and submerged if it leaks you will soon be able to tell

[scottly]

The diaphragm on the side is the "air cut-off valve"; it affects idle if it doesn't function properly. Check the float needle seat for damage or built up varnish. Also, you can measure the fuel level in the float bowl with the carb on the bike by attaching a clear tube on the spigot on the bottom of the bowl, holding it up next to the bowl, and opening the drain screw. The fuel will rise in the tube to the same level as inside the bowl.

[Iainhugh]

It's a brand new needle valve that I fitted. The bike runs absolutely fine. My bro took it for its mot today and it failed on the headlamp not working. Typical because it worked fine last night. 
Anyway if the needle valve isn't seating right what are my options. The more I think about it the more I think this is where the trouble lies. Do I buy another one and see if it works any better. Could the problem also be the valve is fine but the little lugs on float might be a fraction out of shape and not pushing the valve completely shut ??
Iain
Scottish highlands

[scottly]

Iain, it sounds like the needle valve isn't sealing 100%; When running, the motor is using fuel faster than the leak. Like I said before, check the seat.
 

[Iainhugh]

Cheers for the advise Scottly. I'll just have to take carb off and have a look
I'm currently trying to fix a grabbing front brake. Disc skimmed and new pads getting fitted over weekend ,
Regarding the seat what am I looking for. The carb was cleaned out and then a new valve fitted.
I'll get it off and inspect it , I'll post my findings
Thanks again
Iain
Scottish highlands

[Iainhugh]

Had the carb off and re checked everything . Put it back on and it's still pouring out.
Floats are fine . The float seat itself has no visual damage , but I remember the old valve I took out had a ring all the way round the rubber tip. So maybe I need to change the seat itself or you mention a build up of varnish. Is there any special ways to clean it. The carb has already been cleaned out when I did the jets.
Iain
Scottish highlands

[triguyracer]

is the float pin engaged in the slot on the float when you reassemble your carb very easy for it to become disengaged when you are putting it back togeather just a thought a long shot but worth checking

[Iainhugh]

Yeah the pin is in fine. I did think of this since the carb is getting moved about to refit. I had bowl on had carb on side shaked about. Pin isn't coming out so it can't be that ..  I'm leaning towards valve seat. Where the bottom of the seat tapers down to the hole the is a ring all the way round the hole. ??
The same mark I saw on the old valve ? Has any one changed one of these? Is it a case of destroy it to get it out. The top of it sits flush with inside of carb ,
Iain
Scottish highland

[scottly]

Is the ring a dark color, or clean brass? It might be rubber transferred from the old needle? You might try cotton swabs soaked in carb cleaner to polish the sealing surface in the seat.

[Iainhugh]

When I'm saying ring it's more like a ring that's been machined. I compared the new valve to the old one and the new one is slightly longer. I'll try the cotton swab with carb cleaner tonight and see if it makes a difference , but it does look clean. I was blowing through carb and lifting floats. It does shut the air flow but not the fuel.
Iain
Scottish highlands

[WTF304]

Sounds like the needle and seat .... have you checked the floats ? .... metal floats usually corrode by the solder joints and if there are plastic it could still do the same. Take the floats out and get yourself a bowl of water and submerge them. You'll either see air bubbles or the floats won't float ..... they'll sink cause they are filling up.

[Iainhugh]

I have spent 3 nights in my garage with this ... and I think I've finally fixed it. I got the old float valve with a small amount of valve paste fixed the old valve in my drill and gave it a few spins to clean up the valve seat. The floats were sticking for sure. I gave the float bowl a sharp blow with a spanner and the fuel stopped. Inside the float bowl were marks where "something" had been rubbing it. This could have been the original metal floats. I cleaned all the marks with 600 wet and dry paper. So all smooth now. I had submerged the plastic floats and they are fine but what I did notice was the bit of plastic that bridges the two halves of floats  together was catching on the brass overflow tube that's attached to the float bowl causing them to stick. I very gently pushed it forward (hoping it didn't snap off) to clear the floats. I've hooked it back up to fuel supply and it all seems good again.
Thanks for all the advise. Don't think I could have handled another night in garage with all the petrol fumes
Iain
Scottish highlands