MG Midget with Twin SU's

[bigjugs]

Hi have recently bought a MG Midget that was a none runner. I have now got it to start. However, it needs the choke fully out to start and when it fires up the revs go sky high and it sounds megger lumpy. I can just can just about regulate it buy pushing the choke in and out but it struggles to reach a tick over. Because the revs are constantly fluctuating. I not sure what to do or check next.

[TWR]

Take off the top of the carb & check you have oil in it, also take off the alloy body of the carb and check the centre needles, they may be bent,loose, mucked up.

[TWR]

I should have asked, are they SU Carbs?

[bigjugs]

Yes they are twin SU's

[logic]

TWR according to the title they are SU.s
I think you are right in what you say, but getting these carbs ballanced can be a right cow, a very fine adjustment on the main jets, and if I remember rightly, you can't access them both without moving something, which alters the ballance when it is replaced, it may well be the air filter, not sure off hand,
Also the slide piston that carries the needle could be sticky-black which would explain the high revs on start up,
also run your fingers along the needle to feel for a ridge where the tavel would have finshed,
It will be well worth your efforts when you get it right,
Good luck.

[logic]

also a gunsons carballancer is a handy tool for ballancing these carbs, I think I still have one if you want it,
as i hope i never need it again.

[bigjugs]

cheers TWR i will have a look at them.

[bigjugs]

cheers logic how much do you want for it.

[TWR]

Appart from smiling at your name LOL Get a tin of RedX & pour into your tank & I would also drop some down the top of the carbs ( Where I menstioned eariler) give that a try, but as logic said the balance can be a right B to get right.

[bigjugs]

Thanks for the ideas. But its hard to actually do anything like the red-Ex treatment as the engine runs so erratically and is hard to just keep it running. I use the lead replacement and octane boost and I believe this contains a cleaning agent�s. I think I need to start by removing and stripping them down. Someone mentioned it could be the balance weights in my distributor that was the course of the erratic revs. They will not steady they just keep fluctuate.

[TWR]

With respect to their advise I would still go for the Carb to sort out your Problem, When SU are right, hey are right, but given chance of imbalance they can be a right Bsdad. Good Luck.

[bigjugs]

Cheers TWR, I will remove them from the car next weekend, strip them, and see if they have worn jets or needles and also give everything a good clean.

I think the mixture maybe too rich as the plugs are always black and wet. Should I screw back the adjusters and weaken the mixture before I put them back on??? Or put them back and test them as they set up now first??

[TWR]

Hi again, as you say give the carbs a petrol clean throughout you will be surprised at the muck that will emerge, The needle valves do give trouble with their insertion, If someone in the past has forced the valve in to the carb body that will bend a supple needle, but if you take your time I am sure you will achieve your smooth Tick-over, Let us all know how you have got on.

[oldhenry]

you have either rich or lean running. do you get smoke when running , or 'hunting'?
the main jets can be adjusted with the brass nut at the base of the carb, below the dashpot. turn down for lean . try adjusting these to get better running,
i assume that you have correct static timing and the firing order etc. and plug gaps,points perfectly set up?
a carbs are the lat thing to really mes up.

[bigjugs]

Hi oldhenry, I bought the car as a none runner. The distributor was off and the crabs too. I have set the static timing as close as I can. The person I bought the car from told me, the points and condenser were new. I have today striped down the carbs and found the piston lifter was missing on one of the carbs. I think it could have been dragging air in through there???
However all the carburettor setting up procedures in the Haynes book are with the engine at running temperature. It now runs but still very lumpy and the revs still fluctuating. However, it is not kicking out plumes of smoke. I am struggling to get a nice even tick-over. I am thinking of putting the manifold and single SU from my Morris Minor onto the Midget engine and see how that runs. Is this a good idea? If it is still lumpy then I should be looking as something else. What your opinions on that please.