Leaking Su Carb Float Bowl

#1
Hi All I have a P6 2000 Sc with a Su Carb
I noticed a fuel weep coming from the Su bowl it would come and go so I changed the gasket and it was still coming and going.
I was trying to adjust the mixture but found the car would just not run right at all and on start up it sometimes ran perfectly but as soon as
it got warmed up it would misfire no matter what I did to the mixture it would not come right and the plugs are going black like its running far to rich.
I have New Dizzy Cap, Arm, New HT Leads New Coil New Plugs and New Electric Ignition so I know that side of the car should be fine.

Going back to the leak from the float bowl I was thinking along the lines that it was over fuelling so I bought a New stay up float and needle and seat and gasket
from SU Carbs so good parts, I have fitted everything and adjusted the float the best I can, I started the car and thought I can smell fuel No joke there I had to turn the car off quickly its poring out when running I think its coming from out the breather whole, the leak is worse with the new parts then the old lol , I have taken it apart now three times and adjusted the arm on the float closer to the float lid, but it makes no diffidence should I adjust it so it sits lower in the float bowl?

Thank you one and all :)
 

sdibbers

Well-Known Member
#2
Do you have a HS6 or HIF6 carb on your SC? I think they’re all HS6’s on the 2000’s?

If a HIF I would suspect the o rings on the cold start valve have or are failing. Otherwise I would look at any problems with a heat shield. When I changed to HIFs on my TC and ethanol was increased on fuel here I had problems with the float bowl boiling due to ethanol lowing the boiling point considerably.
 
#3
Hi Sdibbers Thank you for your reply I have a HS6 Carb never had any problems with it getting on the hot side
I cant seem to make any scene of whats going on with it, I have tried fitting my old float and still have same problem,
float rises against needle that should cut the fuel off when the bowl is full its like far to much fuel is racing into the bowl
and it looks like its coming out the breather whole.
I did wonder just above the breather is where the petrol pipe joins on there is a copper pipe I wonder if that has gone and its making it look like the fuel is coming out the breather pipe :oops:
 

sdibbers

Well-Known Member
#4
I know you have new parts in there but have you tested the float valve? Take the float chamber cover off the car and turn it upside down. Try blowing throw the input pipe. It should be sealed. If you can easily blow through the pipe the float valve is most likely still leaking.
 
#6
Thank you sdibbers for the info and the video well today I have tried everything from swapping different needles to floats ect
in different order no luck at all still leaking like mad.

So I have removed the carb wow whats the secret to the nut at the float bowl that holds the carb on you cant get a spanner in there I had to use
a 13m flex head ratchet spanner it worked just, So looking at the carb it needs some working doing there was silt in the bottom of the float bowl and even a bit of old gasket must have been in there for years :oops:
I am not sure if I should have a go at restoring it with a kit or send it to Su carbs for restoration as they will blast it clean the kit is about £100 with the dreaded vodka and tonic or a professional rebuild £200
 
#8
It looked better on the car honest :rolleyes:
Where the butterfly is there is black soot on one side of the cylinder wall is that normal?
 

cobraboy

Well-Known Member
#10
Hi All I have a P6 2000 Sc with a Su Carb
I noticed a fuel weep coming from the Su bowl it would come and go so I changed the gasket and it was still coming and going.
I was trying to adjust the mixture but found the car would just not run right at all and on start up it sometimes ran perfectly but as soon as
it got warmed up it would misfire no matter what I did to the mixture it would not come right and the plugs are going black like its running far to rich.
I have New Dizzy Cap, Arm, New HT Leads New Coil New Plugs and New Electric Ignition so I know that side of the car should be fine.

Going back to the leak from the float bowl I was thinking along the lines that it was over fuelling so I bought a New stay up float and needle and seat and gasket
from SU Carbs so good parts, I have fitted everything and adjusted the float the best I can, I started the car and thought I can smell fuel No joke there I had to turn the car off quickly its poring out when running I think its coming from out the breather whole, the leak is worse with the new parts then the old lol , I have taken it apart now three times and adjusted the arm on the float closer to the float lid, but it makes no diffidence should I adjust it so it sits lower in the float bowl?

Thank you one and all :)
The part that is giving you problems is not shown in all your later pictures - the float chamber lid and float etc.

The key to this has to be float height setting.
Assemble the lid with the new stay up float and new needle valve and seat, making sure you fit the washer under the new brass seat then invert the lid so the float rests on the needle valve, now blow through the fuel inlet hole - does the float totally shut off the fuel inlet so you cannot blow through it ?
If not you have to investigate why.
If it does now bend the float so that when the lid is INVERTED you can get a 3/16" drill bit between the float and the lid.
Now assemble and try it.

The only other thing that can go wrong is if you have too much fuel pressure from the pump. Test with a pressure gauge and if the pressure is less than 3 psi you should be OK. Over 3 psi and the carb will likely flood.
 
#11
Thank you guys for your response that is interesting when I removed the old seat there was no washer
but when I inspected the lid there was a perfect shiny circle like one had been there under the seat.

The kit I got also did not come with a new washer.
I have looked at my manual, I could no mention of a washer under the seat in my book?

I have two floats the brown one is the old one, this one seems to set its self to the correct height automatically
and I cant see any way you can adjust it.

The new black float you can bend the arm to get the correct height.

One other question the butterfly when its in the closed position should it shut off the cylinder as mine can not close all the way there is a gap
I put a torch behind so you can see?

The spindle has a little bit of play left and right is this normal?, how do I check to see if it needs re-bushing?
 

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cobraboy

Well-Known Member
#12
You should have a washer under the needle jet, it will raise the fuel level if missing.
The butterfly is likely being held open by the idle speed screw.
If the spindle has side ways movement in its bore in the body then it will need re bushing.
 

cobraboy

Well-Known Member
#13
I just looked in a kit I have for HS carbs and I see no washer for the needle valve, I am not going to look in my carbs. I may be getting confused with some Weber DCOE carbs I have just been working on.

Did you try the test to see if the valve will hold pressure when upside down ?
 
#15
Thank you cobraboy for your reply, I will sound like a complete prat if I have got this wrong:oops:
I have spoken to Su Carb today and they have said there is no washer under the seat :oops:
The Diagram you have provided is a good one But it shows 3 washers needle and seat I think
whoever drew such a diagram was trying to indicate the 3 washers that go under the three nuts /bolts on the float bowl lid
I am not saying your wrong as I still have a perfect circle bigger than my seat on the float bowl lid like a washer used to live happily
in the carb by the fuel I was providing it but now like a old friend is now missing its fuel flow.
 

cobraboy

Well-Known Member
#16
The three washers and jet to one side pictured are for a grose jet, this is an aftermarket jet to help with flooding issues, the washers will be for height adjustment.
It is good that you have confirmed that the stock jet does not have a washer, apologies for the wrong lead on that.

Are you getting anywhere with it ?
 
#18
wow I did not know they made such a jet that's far better then this set up thank you so much.
no need to apologise I appreciate your help and I think we had crossed info on what we was talking about your info is
spot on thank you.
I did buy a new needle and seat but found it did stick a little when bench testing and its brand new :oops:
The carb is still in bits I am at a crossroads with it to be honest there looks like there is ware to the rod.
I could buy a new gaskets and new jet and Rod but I am concerned about the bushes and just how worn they are
my OCD is kicking in I think:p I just dont know if I should spend X amount of money on the bits for the carb
that is going to save a bit of money but not a lot and I will still might have worn bushes no one likes a worn out bush :p
I might be able to get away with a new rod/shaft for sometime or just send it away and have the thing re built with all new parts
and re bushed tested and cleaned for a extra few pounds what do you guys think ?
 
Last edited:

Tom W

Active Member
#19
Everything besides the re-bushing can be done at home. If it does need re-bushing, I think you can get just that bit done at Burlen, then complete the rest of the rebuild yourself.
 
#20
Grose jets were a mixed blessing for me. I ran them for awhile, with generally good results, but then I had some trouble that was cured by going back the viton tip style. For the life of me I can't recall whether it was sticking or flooding, but it was one of the two. I was very disappointed at the time, as I fully bought into the concept.

Yours
Vern
 
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