Weeping carb

[stag36587]

In my quest to finally finish off my restoration I've noticed that there is a small leak from the carburettor jet. Also the jet doesn't return fully "home" without a gentle push.

Looking through past posts it looks like this may be just a case of the jet needing 'centring' and for me to check the jet bearing gland washer or is there another likely cause? Thanks for views.

[mogbob]

Is the leak coming from the base of the float bowl, where the pipe ( supply fuel to the jet ) exits , allowing fuel to run down
the exterior of the tube, dripping from the jet base ? Or , is it leaking out of the main carb body , from around the adjustment nut spring area ?

My assumption is it's a standard SU ..HS 2 carb AUD13 model.
Second scenario ....the washer in that set up is AUC 8478 ( 95p from http://www.moss-europe.co.uk).
First scenario ...I'm not sure that the tiny washer on the end of the jet tube is available separately , It might be a case of going for a gasket set ( Moss AUE 810A £3.65 or Burlen Ltd either http://www.burlen.co.ukor http://www.sucarb.co.uk, both get you to the same website, AUE962 £5.88 inc Vat ).

What state is the carb in currently ? In need of a full strip down and clean ( ? ) or if you want to "cheat " for the moment you could remove the jet assembly alone for cleaning and reassembly. Be very careful with the small union holding the jet tube into the base of the float.It is quite delicate, relatively speaking , and the ham fisted fraternity can easily cross thread the union , trying to force it back in. A blast of carb cleaner ( out in the fresh air ) on the stripped down parts should enable you to find clean metal again.
Reassemble, check oil level in the dashpot.Wind the adjusting nut fully in and then back off 12 flats , i.e. 2 complete revolutions to give you a basic starting point for tuning.Use the lift pin to check that the piston falls freely.
Bob

[stag36587]

Thanks Bob, the leak is only coming from the jet assembly, I'll try to have a closer look later.

[bmcecosse]

Just nip it up slightly - but also check there is free-play on the 'choke' to allow the jet to rise up fully.

[stag36587]

Thanks Roy. I took carb off the car to have a closer look and found that the brass washer between jet bearing and lock nut is missing so I guess that's one possible explanation! Should I seal with anything else too though?

Otherwise, piston moving up and down ok but perhaps a little tighter than I would have expected, the jet is also not as free as I would like. I hooe they both just need careful cleaning.

[mogbob]

The missing washer is probably the clue you were searching for ! Sealing with anything else shouldn't be necessary.
Just proceed , as you planned , with a good gentle clean. Carb cleaner , nothing else that is abrasive.
The piston does need to fall unrestricted but it also needs to hold a bit of suction for 5 / 7 seconds ( appropriate manuals describe the test ).
The jet tube should move under " gentle pressure " but " force " suggests all is not right.Just play around with the cleaned up part to get a feel for it.
In both cases it is easier to demonstrate for someone but not quite so easy to describe accurately the fine line between too much and too little.
Bob

[bmcecosse]

If it's not been used for quite some time. it's probably 'dried out' and may come ok with use.

[stag36587]

Thanks Bob and Roy. Have ordered the washer and given the carb a good clean so will hopefully refit early next week

[stag36587]

Thanks again guys. Carb refitted today, everything adjusted and engine running smoother than ever - and no leaks

[bmcecosse]

Well done - although can't see how a 'washer' would make the difference.....

[mogbob]

Well done that man !
Bob

[stag36587]

Well done - although can't see how a 'washer' would make the difference.....

Me too but then again I also spent a long long time cleaning everything and re-centring the jet so that may have helped.

[bmcecosse]

I suspect so...