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Discussion Starter · #1 ·
Dear all
I have a silver shadow 1972. Recently there has been a discharge of petrol as soon as the ignition is switched on. The flow seems to come from the overflow pipe from the carbs. I think i need to check the floats, needles etc and to do this i am thinking its probably best to remove the whole carb assembly and do a service/clean up on the work bench.
i have reard in manuals and seen on you tube that its fairly straightforward since there is a single bolt holding the carb assembly to the manifold. But does anyone have a step by step guide ot removing linkages, pipes etc?
Any advice greatly appreciated
 

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Others with these cars will post where to download the manuals and such, but the most important thing is to take lots of photos as you disassemble it with notes.
Mark any wires as you disconnect them, don't take it for granted that you can remember where they go.

Don't touch the choke settings.
 

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Yep, the bolt in the center is what bolts the carb assembly to the intake manifold but there's a bunch of stuff that needs to be unbolted from the assembly like the linkage and fuel lines before you can remove it. Here's a quick video that I did back when I had my SS2.

It's quite an involved job

 

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Alabbasi, did you figure out where the vacuum lines went ?
I can't help my self, your video is a great example where one should mark where the vacuum lines should go as well as to take photos.
I use masking tape and a Sharpie myself.
 

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On the Shadow I's it is much easier to just remove the tops from the float bowls and replace the needles and seats and floats if it is flooding. It could very well be that a float has developed a leak and has sunk causing the flooding in which case you can just repair or replace that float and fix the fault. You can also remove the dashpots and clean them inside carefully with a soft cloth and brake cleaner. You don't gain a lot by removing the whole carb assembly unless you want to start replacing throttle shafts or butterflies. Check and replace the little filters in the fuel inlet at the float bowl lid, you will find them when you remove the fuel inlet pipe. Al's video shows the later Shadow II carbs which have the float bowls integral with the base of the carb so the float needles and seats etc cannot be serviced without removing the whole assembly from the engine on those models.
 

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Hi pclackett

The carbs in the youtube video are from the series 2 cars and are different to the ones on your car. The good news is the carbs on your car (SU - HD8s) have the float chambers "external" to the main carb body. You can just undo the fuel lines, pull off the rubber overflow pipes, undo the central bolts and pull off the float chamber lids giving access to the floats and needle valves. I have arrowed the relevant bolts/unions in the pic. The pic shows the carb assembly off the car but the above work can easily be carried out with the carbs in-situ.

If you do decide to remove the whole assembly to recondition the carbs let us know and we can give details on how to do that.
 

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Discussion Starter · #9 ·
[Dear Geoff
many thanks for that! i was wondering if that might be a way forward
regards patrick
 

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Discussion Starter · #11 ·
Hi all and thanks for your advice so far. So I opened up the float chambers on both sides - not needing to take the carb assembly off thanks to Geoffs advice.
So the flotas are brass drums - they seem to float free, submerged about 50%. i took each out and they seemed empty of petrol. The float needles seemed to move ok. The gaskets were perished/very old.
I put the chamber lids back on, reconnected the fuel lines and overflow pipes etc and started up. After a sort of churning noise which i guess is the fuel system re priming, i got the same petrol leak underneath - seemed to come from the overflow pipe.
I am wondering whether I go ahead and replace floats, float needles and gaskets anyway ? Grateful for any views
patrick
 

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"On the Shadow I's it is much easier to just remove the tops from the float bowls and replace the needles and seats and floats if it is flooding". I guess I wasn't clear enough in my post. I meant that unlike the Shadow II's, the Shadow I carbs do not have to be removed to do this.
Did you shake the floats? If any fuel inside you will hear it. Did you remove the float lever and check the condition of the float needle? Was the seating end showing any grooves or ridges? Was the float lever itself showing wear at the hinge pin? Did you find small filters in the housing? Were they missing or clogged with crud?
 

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Hi Patrick

I was curious as to what you meant when you said there was "a sort of churning noise which i guess is the fuel system re priming" .

When you turn on the ignition on a cold engine you should hear a ticking noise from the fuel pump. I mean ignition on but engine not running. If you hear a whirring noise a previous owner may have fitted a non-standard fuel pump, in which case the fuel pressure may be too high and forcing the float down, causing the overflow. This is worth checking after you have carried out all the checks Jim has outlined. I'm just thinking if all else has failed, it could be a fuel pressure problem.

The other point is have you confirmed the leak is from the float overflow. You said the leak "seems to come from the overflow pipe from the carbs" Try pulling back the overflow pipe with the ignition on but engine not running to see if fuel is coming out of the overflow. Take precautions of course - cold engine and oil rag to catch any fuel that comes out.
 

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Discussion Starter · #16 ·
"On the Shadow I's it is much easier to just remove the tops from the float bowls and replace the needles and seats and floats if it is flooding". I guess I wasn't clear enough in my post. I meant that unlike the Shadow II's, the Shadow I carbs do not have to be removed to do this.
Did you shake the floats? If any fuel inside you will hear it. Did you remove the float lever and check the condition of the float needle? Was the seating end showing any grooves or ridges? Was the float lever itself showing wear at the hinge pin? Did you find small filters in the housing? Were they missing or clogged with crud?
Hi Jim
thanks for this, i did shake the floats, no fuel inside. I will now remove the float levers and do the other checks you have recommended, many thanks patrick
 

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Dear all
I have a silver shadow 1972. Recently there has been a discharge of petrol as soon as the ignition is switched on. The flow seems to come from the overflow pipe from the carbs. I think i need to check the floats, needles etc and to do this i am thinking its probably best to remove the whole carb assembly and do a service/clean up on the work bench.
i have reard in manuals and seen on you tube that its fairly straightforward since there is a single bolt holding the carb assembly to the manifold. But does anyone have a step by step guide ot removing linkages, pipes etc?
Any advice greatly appreciated
Hello, had the same issue. Sounds like a float may be stuck. I would get a rubber mallet and give the carbs a good bang. This worked great for me. M
 

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Discussion Starter · #19 ·
ps all, just checking floats which seem ok. Just a question; with the right hand side float chamber - viewed from rh drive drivers seat - there is a sort of vent hole attached to the bolt that secures the float chamber top to the bowl. What is this? is it just for venting or does i have to be connected to anything?
pics to follow
 
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