Why engine keeps flooding?

[bmcecosse]

I asked about the piston movement ages ago........ But - another carb has been tried with same result - so for me - it's NOT the carb!

[Super Mario]

If you lift the carb piston with your finger does it drop onto the bridge with an audible clunk?
AN is a standard needle for 1098 or 1275 twin carb engine.You beat me to the answer Roy.
I think we are missing the "bleeding obvious" which a couple of photos may reveal.

yes it drops with clunk and i think i am missing the obvious too.

[mike.perry]

It is almost impossible to flood an SU carb as long as the float chamber needle valve is working. The only fault is usually too rich a mixture, too much choke, when starting.
Fuel can only enter the cylinders if it is sucked in and then the fuel /air mix is automatically metered.
Just a few random thoughts

[beero]

How does it run with the air cleaner off? Sounds like it, or the can are blocked not letting any air in.

[bmcecosse]

The engine runs for 20 or 30 seconds - at 'high revs'. It can only do so if it can suck in air - so either there is a hole (un-blancked servo connection - faulty manifold gasket ?) or the carb is set with the throttle open.........

[kennatt]

is it definetely petrol coming out of the plug holes,its not a mix of petrol and or water is it collect a little on a rag and see if it burns rapidly

[katy]

[quoteEngine is re-conditioned and has never really run][/quote]
I would recheck the valve timing. Just because both valves were closed when #1 piston was at TDC doesn't necessarily mean that it is correct. The timing chain may be out by one or more teeth.

[bmcecosse]

It "runs for 20 or 30 seconds" - - or I would agree!

[MarkyB]

"completely filled with petrol" after 5 seconds has to be an exaggeration.
Even putting the petrol pump outlet pipe into the throat of the carb wouldn't achieve this.

Running very fast for a short time does suggest rich mixture/ air leak.
Wet plugs suggests failing spark, unless the ignition is being turned off at high revs and mixture is being pulled into non firing cylinders.

I'd start by disconnecting the throttle and choke cables then winding out the tickover and fast running screws.
Then see what happens.

Even better to hear from dad!

[mike.perry]

I would still like to see some photos

[simmitc]

I agree, a picture is worth a thousand words.

Is it definitely pure petrol coming out of the bores? Could any of it be water - how is the level in the radiator before and after running the engine?

With the plugs removed, how does the liquid come out of the bores? Is it a small squirt as the pistons rise, or does it literally flow out of the plug holes?

[bmcecosse]

[kennatt]

was this ever resolved

[Super Mario]

Thank you everybody for their help. It turned out to be carburretor problem. My Dad did try and explain what the problem was but it went right over my head

[mike.perry]

Having delved so deeply into the subject could your dad explain it to us and put us out of our misery?

[bmcecosse]

Indeed - we are 'dying to know' - since pretty much everything possible was suggested - and rejected - earlier.

[Super Mario]

My Dad said that the fault was in the carburretor but he couldn't find what the fault was.

[bmcecosse]

Did he not try two different carbs early on ??

[aseriesade2]

THE ONLY TIME I CAN RECALL SEEING THIS FAULT WAS WHEN THE FLOAT NEEDLE VALVE WASN'T SHUTTING OFF THE FUEL MEANING THE PETROL IS PUMPING IN UNDER PRESSURE (SO LONG AS IT DOESN'T LEAK OUT OF THE TOP OF THE FLOAT BOWL AS PER NORMAL)MEANING THE MINUTE THE IGNITION IS LIVE IT THEN FLOODS THE ENGINE BY OVER PUMPING THE FUEL WETTING THE PLUGS REMEMBER BY THE TIME YOU SHUT OFF THE IGNITION IT HAS PUMPED IN EVEN MORE PETROL PARTICULARLY WHEN YOU HAVE TRIED TO START IT A FEW TIMES WHEN IT FLOODED. THE ONLY THING I DON'T GET IS TWO CARBS WITH THE SAME FAULT ????? ALSO YOU WOULD HEAR THE PUMP GOING LIKE MAD TAKING UP THE SLACK WHICH WOULD BE A DEAD GIVE AWAY ????? ALL I CAN SAY IS WITH PETROL AT ITS CRAZY PRICE ITS A FAULT YOU COULD DO WITHOUT.

[bmcecosse]

Yes - well we asked all about that first time round - it was said to be still 'doing it' with the fuel pump disconnected........
Personally - I think it was just flooded with too many attempts to start it - possibly with HT leads wrong or an ignition fault - and then it can be a bu99er to get them going again!