Carb dribble

[jreacock]

On the whole - the Beta is going fine and I'm still running it in after the rebuild. One thing I've notice though, is that it starts up fine from cold (I've got a rough patch between the chokes - but that's something that I've got used to), but after a switch off of a few minutes, it's hard to start back up. Today, when I parked up at work (it's a dry day) - I whipped the top off the K&N, and noticed petrol slowly dripping from the accelerator pump, and it was pooling up a bit on the butterfly on both sides. Maybe a drip every 10 seconds. As far as I know, the fuel cut-off solenoid is working fine, my electric fuel pump is set to whatever it should be (can't remember - Guy Croft gave me the pressure to set), and the carb is all rebuilt and clean. It's an auto choke, and this seems to be operating fine. I notice a feint whiff of petrol as I'm driving as well - if the window's open. The carb seems to have gradually changed to this mode of operation, rather than it being like it from the rebuild. I've not made any changes to it that would have caused this - although, I did try to turn the idle mixture screw last night (thinking it might be set wrong), but it seems to be quite hard to turn, so I left it alone.

Any ideas?

[Kevo]

Fuel return line blocked?

[jreacock]

The fuel return line has been blanked off - which was something that had to be done for the electric fuel pump conversion. Without the mod, it wasn't possible to achieve the pressure that was specified. I got the kit from Guy Croft, and he let me know about the return line. This dribble happens when the engine is running, and also after it's all stopped (and the fuel pump is off). The carb may be warm - I haven't really checked it, but it has an insulation block as you'd expect.

[Kevo]

Agh should of thought it would be blocked off when you mentioned electric fuel pump, sorry didn’t engage my brain.
Sounds like you may have to strip and clean the carb down.

[jreacock]

Yes - that's probably going to be the thing to do. I have a spare carb that I'm going to clean up and then swap. I think the spare one was actually the one that used to be on there - and I mixed them up when everything was taken off. Should have taken more pics before disassembly.

[Neil-yaj396]

In the rebuild has the accelerator pump diaphragm, and any other bits, been tightened up properly? I had a problem when fitting a new diaphragm that it came slightly loose after a few weeks, though my drip was out of the carb onto the manifold.

[jreacock]

Thanks - I'll check that. It has been a gradual change, so it could easily be something loosening off with use.

[WestonE]

The accelerator Pump Jet has a ball valve built into it you may just need a new pump jet. I hope that helps along with Fast Road Cars on the internet will have the part.

Eric 

[squiglyzigly]

Might be worth re-checking the float height, and if you can, the fuel pressure. If the pressure is much more than 3-4psi you might be forcing fuel past the float valve.
 
It is possible to run a return line with an electric pump and has some benefits. Some electric pumps (facet red/silver tops) can overheat without a return and cavitate within the pump at low demand, e.g. sitting in traffic.
My vx runs a return line with a facet red top and has a simple choke in the return line with a 130 (1.3mm) fuel jet from a Weber dcoe carb. Constant 3psi at all times and a gentle flow through the pump to keep it cool.
When it was run without the return, it had a similar dribble problem as yours from time to time causing hot starting problems and a pong. 

[jreacock]

Thanks for all the suggestions. It's very useful to have a list of things to check for.

I changed the carb yesterday for a spare that I'd blown through with compressed air and carb cleaner. It's off an HPE donor car that I salvaged spares from - when they were cheap. The main jets have the same numbers on both carbs, and there's only a tiny cosmetic difference between them - some kind of lever on the accelerator pump which I had to remove. During the road test, the spare had the same rough patch between 1700 and 2300 rpm, and generally ran a bit lumpy all round. So - today, I cleaned the original one back up. I found a very fine silty (rust-coloured) layer in the float chamber. The filter king has let it through - so I guess the particle size is very small. Cleaned it all through and checked and cleaned the pump and pump jet.
I took it out after, and it does seem to be much better - the rough patch appears to be reduced in both its range and severity - and the hot start issue has gone. Anyway - I'll see how it goes and update if there is any significant change.
Thanks again.
Justin.
 

[mwredit]

I had problems with dirt particles in my carburetor over and over...until I dropped the tank, cleaned and coated it. After that, the fuel system was clean as a whistle.  It's amazing what these filters allow through, except boulders and medium sized birds.

[peteracs]

I guess that is why folk spend real money on a Filter King or similar.

Peter