Weeping carb

[mobylette]

Any advice as to what is causing this weeping at the junction of the main jet and the feed from the float bowl? The flexible pipe looks dry at the float bowl end. Carb is an HS4. Thanks.

[svenedin]

Inside the anti-kink spring there is a nylon pipe. It is most likely to be coming from the union with the float bowl and trickling down to the lowest point. At the float bowl end there is a O-ring inside that can fail. This O-ring is now Viton but formerly it was rubber. The rubber one is vulnerable to ethanol in petrol. Nylon is not affected by ethanol.

Changing the O-ring is possible (but tricky) with the carburettor on the car. I recommend you watch this video as it is very easy to get wrong and straightforward when you know how. If you have reason to suspect the jet may be worn it may be better to fit a new jet and tube which will be supplied with a new O-ring. My experience is a jet can be changed without re-centring being required but do check for the piston clunk to check all is well.

https://youtu.be/ZPzu2zzyGCQ

Stephen

[mobylette]

Thanks Stephen, I think I will whip the carb off and replace that O ring, might as well get the viton tipped valve for the float bowl while I am there

[svenedin]

Thanks Stephen, I think I will whip the carb off and replace that O ring, might as well get the viton tipped valve for the float bowl while I am there

You're welcome. If changing the float valve seat a special thin walled box spanner is needed. It's 11/32" AF but an ordinary socket will get stuck. The tool is available from SU and carburettor specialists. Rather expensive for what it is. If you have the skills you might be able to thin the wall of an ordinary 11/32" socket to fit. Remember to set the float gap correctly after replacing the needle.

https://www.scparts.co.uk/sc_en/box-spa ... 98172.html

[geoberni]

I wonder if this would do the job?
https://uk.rs-online.com/web/p/sockets/5094252

From the data sheet, the diameter at the working end is 12.1mm.
11/32 is 8.73mm, so that would give a wall of between 1.5-2.0mm

It works out at £15.56 inc shipping, against £35.26 inc shipping for the box spanner...

However, looking at this Moss Video, I suspect it may just be 'luck of the draw' on whether a socket will be too large.
Possibly a cheaper socket will already be thin walled enough
https://www.youtube.com/watch?v=NVLhUC-fKc8

[philthehill]

The correct jet spanner cannot be more than 12mm O.D. x 19mm reduced dia length otherwise the spanner will not fit around and over the needle jet body.
The body thickness is 1.1 mm.