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MG Midget and Sprite Technical - Running badly - where to start?

Hi
Was looking for a little inspiration. My 948cc standard frogeye hasnt been run for about 7 or 8 weeks. Went to start her up today and she really struggled to start, and once started, it ran badly and the revs refused to go above 1500rpm.
Last time out it ran fine, so what I dont understand is what can go wrong just sitting in the garage?

The only thing I can think of is not long ago I did have a problem with petrol overflowing from one of the su float chambers, but I opened it up, put the needle back in (as it slipped out) and it ran fine.
Should the needle stay in situ when you resite it? Mine falls out and I have to hold the float fork in place to stop it dropping out whilst putting the lid back on the chamber.
I realise that because I think its the carbs its more than likely the electrics........
Graham V

At the hinge end of the float fork there is a small tab that can be bent upwards (towards the float chamber lid). This limits the opening of the float valve and prevents the needle from falling out.
Simon
Simon Wood

If it was running well previously and has just been parked since then, don't start just adjusting things. If you have already done work, then suspect the last thing that you did! Things don't go out of adjustment randomly, or wear out whilst it is sitting still! (Not including Simon's good advice about the float hinge as that could have been wrongly set before).

I would check things that might stick, like the float needle, throttle and choke levers and so on. And I would check things that might have got damp or corroded whilst unused. Dry out the inside of the dizzy cap. Wiggle or remove and clean electrical connections on the ignition circuit and HT leads.

If you can get it running, then try disconnecting each plug lead in turn - using insulated pliers! - If any one, when disconnected, DOESN'T make it run worse, then that cylinder is the one not contributing to the engine running, and is not firing properly.
Guy W

Presuming you replaced the float needle the correct way round of course! Easy mistake to make! :-)
Guy W

Graham...hope the reason for not being run was nothing truly untowards...but the best maintenance is use...hence the reason I drive mine all year round..Dave
David Cox

Dash-pots empty?

Jim
J Smith

After a year or so of putting the car in the garage, fixing something running up the engine to check my fix worked then working on something else I recognised that the car always ran far far worse when coming out of a break.

Its taken me a lot of thought to come to the conclusion that the 'running it up' means heavy choke for 10 minutes, and what I've been doing is fouling the plugs (can you foul the cylinder head too?)

and the only way to fix it is what I believe is known as the "Italian Service" in some quarters - ie go and rag it - high revs, low gears, after about ten minutes the temperature comes up, rough running goes away and we're all sweetness and light.

getting to the position though where you can run smoothly enough to administer the service is a bit painful, but I've found that taking the plugs out and giving them a clean and re-gap helps - as does remembering to not leave it parked with the choke out - message received on that one

Might not help but if you've been in the garage trying hard to get it going, have a cup of tea and cleaning the plugs is therapeutic!
timmyk

I've heard of the "Italian service" years ago but not heard it called that. The guy mentioned that they regularly had things like FIAT twin cams come in that had just pottered around locally with not real load on them and that wasn't good for keeping them running sweet so one of the first things they did was take it out to a local fast road and cane the engine which normally improved things. These days I doubt it would work due to the traffic on that road now.

I wonder if that is what I saw on my Sprite once after a brief caning I pulled in to the house and when closing the gate I noticed glowing embers popping out of the exhaust pip, the engine was running fine and continued to do so. I suspect it was the result of crap breaking off the back of the inlet valve and burning through the engine. I'd seen in the past when inspecting valve that often large sections of the crud build-up had broken off. It can't be good for airflow.
David Billington

..like I say: use it or lose it...
David Cox

David and David your comments totally resonate for me.
Years ago I had a Lancia 2000 Volumex which I used as a commuter. It rarely got out of the city (Aberdeen).

I was in despair because it was running so poorly and then I thrashed it to the south of Spain and back with my father-in-law as the passenger, picking up 3 speeding fines on the way (all in France - the Spanish cops didn't give a damn).

It ran great after that until I sold it. I wish I still had it but the insurabce got too expensive.

More recently I rebuilt the head off a Sabre diesel from a fishing boat. The fouling was the worst I've ever seen, but the worst was on the inlet valves and in the inlet chambers in the head. I couldn't even see the tips of the guides.

The present owner and the PO both told me they didn't like to thrash the engine. 8 knots is good enough they said, but I fished aboard this boat 20 years ago and I know she'll make 15 knots.

So the lesson for me is Drive It Like You Just Stole It. You and the car while both enjoy it.
Greybeard

BTW here's No2 inlet from the Sabre before cleaning. This was one of better ones.

Greybeard

Hi
Thanks for the very helful comments, especially the earlier ones, as until now in my 8 years of ownership, it has always started perfectly.
Unfortunately I have done something to my back, so crouching under the frogeye bonnet was not on the agenda for today. As soon as the back improves a bit, I will jack the car up (those who have a frogeye will know why it helps to do that to work on the carbs!)and take a look, especially to see if I can do what Simon says, and because Guy's advise makes sense to me in that my most recent tinkering is most likely to be the problem.
I will report back - thanks
Graham V

This thread was discussed between 24/01/2016 and 25/01/2016

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