Hi all

Went to take my cooper s for its weekly drive and when I started it heaps of black smoke came out of the exhaust. It has the standard twin su's

I checked the spark plugs and found then very wet.

It appears to be flooding.

Any ideas before I take it to the mechanics?

Flaot needle valves sticking from lack of use and SH1T fuel

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Hi I always use bp premium fuel and only had the carbies overhauled recently.

How do you fix the floating needle problem?

You can buy a grose jet style needle valve to eliminate this.
http://www.7ent.com/products/grose-jet- ... e0045.html

sounds like you should take it to the mechanic...



take the float bowl lids off, turn them upside down and blow through them (with your mouth, not an air compressor)

if you can blow through them, then the "needle and seat" is faulty, and the person who overhauled them needs to have another look

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In hot weather the fuel in the float bowls can evaporate out and it leaves a dry residue which can flake off and sometimes it can block the needle valve open.
Often a whack on the float bowl with the handle of a screwdriver is enough to clear it up.

Check the choke isn't stuck on
Just because the choke is pushed all the way in doesn't mean the jets have returned to the run position. The mechanism can get sticky.
Dave

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Good call.

A couple of suggestions.
As others have said choke mechanism sticking with choke ON. Happens to my S every now and then.
Wrong size float needle.
There are several size and type of float needle and seats.
You only need the smallest float needle size - IIRC 0.096 " WRONG this is for the large hole size - 0.096"/3/32".
Wrong float or fuel level either not set at all or set incorrectly.
If you have the all plastic type of float the fuel level is set by adding 0.010" aluminium washers under the needle seat.
There is a part number for them but I can't find it just now. Its in a very safe place.
You still have to check the level with a 1/8" drill bit between the float lid and the float whilst holding the float lid upside down.
In most cases you will have to add washers to get the correct fuel level.

Edit: Finally found my SU/Midel catalogue circa 1993 or earlier.

The 0.096" needle and seat is for the Large size needle and seat - AUD9096 spring loaded and AUD9585 Viton tipped.

The 0.010" washers for adjusting the float are: AYB 0377.
the AYB prefix seems to suggest it is a BMC number rather than an SU number.

Hope this helps
RonR

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68 build Mk1 Cooper S
72 Clubman GT project. Total restoration required

and if the floats have fuel sloshing around in them, they have a pin hole some where

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And if the needle and seat is not sealing properly, you would normally have fuel leaking out the breather on the top of the float bowl lid, as well as running rich.

Thanks for all the suggestions

I have a feeling that the choke is stuck so I will have a go this weekend at trying to get it to its proper position.

I assume that means butterflies up? Any photos would be greatly appreciated.

SU carbs don't have a "choke" butterfly.
The choke works by moving the main jet down to provide a rich mixture for cold start.
To check this make sure the choke knob is fully pushed in and then get your fingers onto the main jet on each carb and make sure it is pushed hard up against the jet holder.

They also do not have an accelerator pump so you can't flood them by pumping the pedal.

Google is your friend if you need to find info on how SU carbs work.

RonR

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68 build Mk1 Cooper S
72 Clubman GT project. Total restoration required

Thank you Ron

Thanks to all. The choke on one of the carbies was stuck. A simple tap fixed it. Found a great picture via Google which did the trick