Leak from front carb-where from?

[tony g]

Hi on my Sprint the front carb has some petrol around the mixture adjuster and jet. Sometimes theres a small spot on the bottom hose. Is this likely to be a washer where the main jet is screwed to the carb body? I want to get this done before I swap to efi so I can use them on another engine.

Cheers

Tony

[tony g]

anyone?
Tony

[Triumph1300]

More likely to be where the feed pipe to the jet, screws into the bottom of the float chamber.

Unless that's where You're referring to?

[Richard the old one]

If the arrangement is the same as on a 1500 engine there is a small O ring part number AUD2194 seal rubber that is compressed when the nut holding the jet fuel pipe in the Float chamber is tightened up. The nut should not directly compress the seal but act on a washer part AUD2193 washer seal supporting. Some times this washer is missing. You may be able to stop the leak by just tightening the nut but if the seal has perished it could make it worst.

[MIG Wielder]

The trouble with petrol is that it gets every where. If Richard's suggestion doesn't work it may be that the float chamber needle valve is starting to fail. Imagine you have just come in from a run. There will be fuel under pressure in the pipes and at the input to the needle valve. When you stop the fuel is no longer being sucked out of the top of the jet and into the engine. So a slow leak will tend to collect petrol at the top of the jet and although the jet / jet holder are quite a tight fit fuel will eventually leak down between the jet and holder and onto the adjusting nut. And of course when all the residual pressure on the output side of the pump has dissipated no more leaks.
Is that carb; running slightly rich ?
If you turn the engine off and spend a few minutes with the dashpot and suction chamber off looking at the top of the jet, can you see much liquid fuel collecting ?
If so, a new needle valve may help.
Tony.

[tony g]

Thanks guys, I'll check the pipe ring first then maybe look at the jet itself. Im on electric pump so I dont think its residual pressure after running but will do as you say Tony and check with the chamber removed

Tony

[Richard the old one]

Tony.

I do not know if you have had time to investigate the petrol leak problem yet but due to the very cold weather I have been looking through some old copies of Dolly Mixture. In edition 133 Summer 2009 I wrote that even after changing the float chamber o ring the bottom of the jet was still damp with petrol and that on closer inspection I found that the jet was actually leaking where the flexible pipe connects into the jet and it was also not the first time I had come across this problem. I do not think I have had the problem again since 2009 so I had completely forgotten about that failure mode. Hence it is also something that you need to consider and check on. If it is the problem a new jet will be required as you can't repair them as far as I am aware.