Just to illustrate what happens to the float valve after several years of usage, the rubber on the tip wears out, does not really mena that there is a debris that got stuck in there but simply quality of the rubber deteriorate in time, it gets pinched and it loses it sealing capacity, no matter how hard the float pushes it , i think the grose float valve is not prone to pinching and it works better., thats what i use now on my mini.

The picture explains all:

An electric pump would also keep flowing as long as the engine was running. However, I suspect it might be a mechanical pump based on the apparent age of the car. My "early" 80's Mini did not have an electric pump or wiring for one. The Haynes wiring diagram for 1988 on carb models does not show a fuel pump or wiring.

My guess is a mechanical fuel pump as it keeps overflowing as long as he can keep the engine running.

Diagnose your overflowing SU float bowl using this one weird trick...

take the float apart and look to see if there is detritus causing it to stick open.

Awful fuel is available everywhere throughout the U.S. and is probably eating its way through various fuel pump parts, the insides of flex hoses and so on in hundreds of cars as I type this. Perhaps a flex hose about to fail is giving up its innards to jam up the needle valve. 

You did not say what kind of fuel pump your mini has. I am curious.

From the first post:  "Hi all! I have a classic mini- I think its a 1992 Rover- with a single SU HS carb mounted on a 998. "

The advice given so far is right on target, start diagnosing the problem through examining the basics, namely the float valve.  You'll find that our host has 2 units available:  CA90 & AUD9096GR (Incidentally, the 'CA90' part number at MSC is for the gross jet, and MSC uses the Berlen Fuel Systems part number WZX 1100 and adds some gaskets to give WZX1100A for the complete kit.)

In the event that the problem lies elsewhere, I'll also suggest that you identify which carb (HS2, HS4 etc.) you have installed, in the event that spare part numbers are needed. 

Check this out - If you've an HS4, there's a nifty picture and some cool part numbers for the ordinary service replacement FZX 3003 carb:

//sucarb.co.uk/carbspec/carburettor/spares/id/1801/ 


If you've an HS2, the same float needle valve is used.

Here's an example:

//sucarb.co.uk/carbspec/carburettor/spares/id/1683/ 

Thanks all for the advice!

So the carb only has about 16,000 miles on it. I'd hate to think the parts have worn in that time. It sure sounds like its flooding, but in any car I'v had previously, once it floods it takes some time before it'll start again- this one starts right up... granted it doesn't stay started....

I was using a little choke to keep it running long enough to get around the front to take a look while it was going. Normally, like you said, I only use it to start and warm it up on colder days.

Other than taking the bowl lid off and giving it a good cleaning, I haven't taken it apart any further. There's fuel in the bowl but not inside the float itself- so it floats. I guess I'll take the float off next and inspect the valve and seat. I can't blow through it in the closed position, but maybe the fuel is leaving through just enough. Thanks all!

As said, the replacement or checking of the valve is pretty easy.

Here is the exploded view:
//sucarb.co.uk/carbspec/carburettor/spares/id/1753/

but checking the valve requires minimal dismantling. 

5

Needle & Seat Kit

VIEW

I pretty much agree with what's already been said  especially the bit about finding the problem rather than splashing cash.

IMHO you nailed the issue right there   "....it's dumping fuel out the bowl overflow and will continue to dump fuel for as long as I can keep it going."  Its a sure sign the carb is flooding...and the engine is trying to overcome an over-rich mixture....

This means the float valve is not working (or you've installed a new pump that supplies far too much pressure) .  If you remove the float chamber lid and hold it upside down (so the weight of the float is sitting on the needle) you should not be able to blow though the inlet... New needles and seats are cheap and easily installed so that would be my first step.  I like the "viton" tipped needles - the ones in my carbs have worked fine in regular use for the last 20 years or so....  although they do sometimes need a clean. 

Cheers, Ian

When not knowing the status of the carb, sometimes a rebuild is a more efficient option time wise.
The SU is a pretty straightforward carb. Burlen Systems has a lot of information online. It is just hard to find at times.

Hopefully John(JEG) will chime in as he seems to be able to find details.
//sucarb.co.uk/technical/

//sucarb.co.uk/technical-hs-type-carburetter-description-adjustments

... exactly what Mur advises.
.

Let's start with the basics. The float valve in the float bowl is a wear item, and yours could easily be 24 years old right now. Was there fluid in the float itself? 

You should only need the choke fully out to start the car and then only slightly out for a faster idle to warm up, and when it is warm outside you probably do not need to warm up the car anyway. Your carb has a spring biased needle that wears at the side of the jet, so, again, these items change dimension over time and are wear items. Your original jet would have been the waxstat type, that moves slightly in relation to temperature. You can replace it with a normal one that has none of that foolishness.

These carbs have no accelerator pump, so if you are pumping madly at the throttle pedal like a redneck trying to keep an aged four barrel V-8 running, well, you are not accomplishing much. 

Normally, since this is an Internet forum, a bunch of fools will now chime in to tell you to fit an electric fuel pump, to change out various ignition parts randomly, and to fit wider wheels. This would help you to have the car out of commission for the entire summer and enable you to go on at length about how difficult minis are.  A local MG specialist shop could then take the car on for several weeks and confirm your recent biases, culminating in a bill larger than forum member Alex spends when building 998s for his pals.

On Monday, call our host. Talk to Jemal. Have the float and jet kit sent by courier. Discover who the real mini folks are local to you and you will likely find someone glad to spend a couple of hours with you sorting this out.

Hi all! I have a classic mini- I think its a 1992 Rover- with a single SU HS carb mounted on a 998. When I start it up with the manual choke, it seems to run fine. But after a couple minutes it starts to cough and sputter then just dies. If I have the choke on at the time, the RPMs will rise before it dies. I can start it again, but it only last a coupe seconds even if I'm pumping the gas. Once I got it in the garage to take a look it appears that even before it dies, it's dumping fuel out the bowl overflow and will continue to dump fuel for as long as I can keep it going. I opened the bowl and its pretty clean. With the float in the up position it does seem to stop air when I blow through it- I'm unsure how much pressure it will stop though. The puzzling thing is that it didn't ramp up to happening, it just started doing this- no decrease in performance beforehand. I checked the dashpot and its filled with fluid. Its been suggested that I do a rebuild but I'd rather not if its a simpler fix. Any help would be great! Summer's here and I'd hate to have it cooped up for the durration.