lummpy running.

[overider]

Hi, I have just bought a MG Midget as a none runner. The distributor was off and the Twin SU carburettors 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. but im not sure if the unit is the correct distributor for the car.
I have today striped down the carbs and the only fault i could find was 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.(this is what i cannot achieve).
I now have the engine running in a fashion but it is still very lumpy and the revs are high and fluctuating. However, it is not kicking out plumes of smoke. I am struggling to get a nice even steady tick-over. If I try to rev the engine, it just dies. I am thinking of putting the manifold and single SU from my Morris Minor onto the Midget engine and see how it then 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.

[PSL184]

Best bet would be an HIF44 on an MG inlet manifold anyway - Twin carbs are a real pain to set up at the best of times - esp if you don't know the history of them....

[bmcecosse]

You should get it running with the twins ok - first check - are the pistons moving smoothly up and down - both carbs ? Do they fall back with a nice clunk after you lift them up with your finger? Are the needles in both carbs identical - fitted flush with the piston base, and not bent? Are the choke controls going right off on both carbs ? Are the fuel levels correct in the float bowls? And finally - separate the interconnection between the throttle shafts (just loosen - don't remove) and then adjust the throttle screws on each carb back until each one if fully closed - then advance them an identical amount. Should start and run - then you can play with the mixture adjustments. Not much point putting the single Minor carb on - what would it really achieve ?

[dalebrignall]

what kind of oil do you have in the dash pots,if its too thick wont rev

[overider]

Hi, bmc and thanks for your help. All you have mentioned I have checked and all seem to be ok. The only thing I don’t know is if the fuel levels are correct in the float bowls. How can I check them? the pistons move up and down smoothly but dont clung down. I used engine oil in the dashpots. The reason I was thinking of putting the single moggy SU etc on was just to see if the engine runs ok with that on. If it dose I know for sure it is the carburettors I should be looking at. Like I said be for I don’t know if the distributor is ok and was wondering if the rev fluctuation was something to do with the balance weights in the dizzy.

[mike.perry]

I am running twin HS2s on my 1275 Midget engine and they are a real fiddle to get even. Have you got an instruction book on setting them up? That needs to be followed exactly.
First though, you need to make sure that both pistons are dropping with an audible clunk. Remove the filters and lift them up with your finger and let them drop. If necessary remove the dash pot pistons and try again. That will remove the oil damping.
I always use 3 in 1 oil which is a lot thinner than engine oil

[bmcecosse]

Yes - the clunk is heard with piston damper removed.
It's a great joy to get twin carbs running nicely - and I found it easy enough - just need a length of hose to listen to the air flow ! Details of how to check float levels are in Minor workshop manual

[overider]

Thanks for the encouragement. I will have another go with them before I hit them with a very large hammer (only joking). It will probably be next weekend now before I have time to try setting them again. I will let you know how I get on.

Just one last thing. It’s the fluctuation in revs that’s bugging me is this a pointer to the carbs or is this something else?...

[mike.perry]

They are probably still not in balance. I still have to refer to the SU manual when I adjust mine. I still haven't got the hang of using a tube but that is probably lack of practise.

[Stig]

Best bet would be an HIF44 on an MG inlet manifold anyway....

I doubt it'll fit without hitting the underside of the bonnet. I fancied that for my Sprite but stayed with twin HS2's because of the lack of clearance. A Midget bonnet's a lot lower than a Minor bonnet!

[bmcecosse]

Yes - the Midget inlet manifold for SUs is much less angled than the manifolds for other A series. Anyway -it's traditional for Midgets to have twin carbs !