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MG MGB Technical - Flooded engine

After my 71B was sitting for a couple of weeks I tried to start it on a cold morning using full choke. It would not fire. After poking around a bit, I pulled a spark plug and found it wet with gas. I put in a fresh set and tried starting it with no choke. It fired right up.

My question is ... I can see the idle speed adjustment screw when the choke is engaged, but is there no mixture adjustment other than how far out you pull the choke? Should it be possible to flood the engine with full choke?
G Nicholas

It certainly is, if for any reason it doesn't fire within a few seconds. You can usually smell the petrol in the exhaust, unless perhaps you are outside and it is windy. If you *do* flood it, then the first thing to investigate is why it didn't start, i.e. check for a spark. To clear a flood with SUs push the choke home, press the throttle to the floor and crank, being ready to release the pedal and half-pull the choke as soon as it fires.

I always start mine cold on full choke but it needs to be pushed in half-way immediately it fires. It quite possibly would start at half choke, except perhaps in very cold weather, but that would mean gauging how far to pull the choke according to outside temperature, and as it has always (except on very rare occasions when there has been a problem, maybe two in 22 years) been a quick and easy starter it isn't a problem to use full choke.
PaulH Solihull

It's quite easy to flood with most carb types. When you pull the cable the first half is the fast idle the second half enriches the mixture, hence the need for half choke when it fires up. I find that full choke is too much unless very cold. I use 3/4's and if it doesn't fire in the first few turn, press the gas pedal slowly to about half way. Seems to work for me!
Getting the correct air fuel ratio for all temperatures with a manual pull cable is a bit of a challenge....
If it persists as a bad starter make sure all the other things are in good order eg. points, plugs etc etc.

MGmike
M McAndrew

Not half for fast idle, only about 1/4" at most if the cable is adjusted correctly, after that enrichment starts.
PaulH Solihull

Thank you guys. I had a recent tuneup which must have changed the cable adjustment on the choke. It used to start easily with full choke. Now I have to find the right amount of choke, and be careful while I am experimenting.
G Nicholas

Once the system is set up correctly, most engines will start relatively easily. I marvel how the GT can sit for long periods yet when it is time to start, full choke, fires, then straight to 1/2 or 1/4 and off we go. Mind you if the float chambers are empty, and battery not good and ignition off then that is another story. Mike
J.M. Doust

Float chambers will fill while you are turning the key through ignition to crank and while cranking. In summer my V8 carbs frequently empty on switch-off, I can hear the fuel boiling and see the vapour pouring out of the vent tube. Pump chatters away when next turning on the ignition but it fires up just the same. Poor state of battery and tune is a different kettle of swimming things.
PaulH Solihull

This thread was discussed between 19/10/2011 and 21/10/2011

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