Midget Running on 2 cylinders

[Lancastermidget]

I own a 1972 MG Midget with a 1275 A-series running standard twin SU carbs. When warm the engine runs superb. I have a problem though when it's cold & running on choke as only cylinders 1 & 4 are running. Taking the plug leads off 2 & 3 when cold & on choke make no difference to rough running but both are sparking OK. As soon as it's up to temperature and the choke is off it's back running on all 4 as sweet as anything.

Has anyone seen this before/got any ideas on what the issue could be?

[Luxobarge]

Moved to "Technical Queries" section.....

[arceye]

First thing I'd try would be a good service of the ignition system, especially if it hasn't had one lately, change plugs, gap / clean points, clean / change rotor arm, same for dizzy cap, change HT leads. Then carry on from there.

You can always change one thing at a time and see if that does it, I recently had a very poor running A series, bad to start, no power until warm, hard to rev and missing etc. Tried most of the above before changing the nearly new spark plugs for an old set I had lying around, problem solved. So even if parts are recent you can not trust them to be good.

That would be my first port of call anyway.

[vintagemotor]

I had a similar problem with my Rover P6, I started it up in the dark, raised the bonnet and the HT leads were twinkling like a Christmas tree! Might be worth a try? A spray with WD40 to displace damp helped but a new set of leads was the long term cure. Just thought it must be worth a go?

[Lancastermidget]

Just resurecting this post. I managed to get to the point where the Midget was running on 3 cylinders when cold but then ran on 4 when off the choke/warm. It was also smoking quite a bit so I decided that I had to take the head off to take a look. On taking all the valves out tonight I've found I have a sticking inlet valve on the cylinder which is the problem, so hopefully should solve my issue. But one thing I noticed is that on every valve I've only got an outer spring, no inner springs at all. Should a 1275 A-series engine have both inner & outer valve springs? Looking at Moss & MGOC spares they indicate it should but before buying 8 of them just wonder if anyone knows for definite?
Thanks

[woblynne]

Hi, originally the Midget/Sprite would have had double valve springs but later A series heads only had the single outer springs with no issues (even the MG Metro head).

Thanks
Mark