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MG Midget and Sprite Technical - Getting a tad angry!

I have had the carbs (supposedly)set up. I have had the electronic points gizmo fitted, but my engine seems worse now than when I started. It coughs, splutters, spits back and pops and bangs now when accelerating. The mechanic who has done the work reckons it is either the pancake filters which are disintegrating (no foam and cracked backs) or worn carb internals.
My new toy is losing its appeal and my wallet is creaking!
What do you guys think? New filters? Original or pancake? Or am I barking up the wrong mechanic?
J Mee

Yes new air filters (original style) and yes... new mechanic.
Trevor Jessie

Honestly, I cannot imagine having a Spridget
AND paying a mechanic at the same time. There
ain't that much cash in the world. Learn
to work on it yourself!

btw - I have often run my 72 with no air cleaner
for short tuning runs. Try that first (yes, you
can do this your own self). If it runs great
with no filters, suspect the filters are the
prob. If it still runs crap, 'taint the filters.

I am assuming you have SUs and that your mechanic
knows naught about SUs.

I have as we all should have a cardinal rule.

Your original problem was down to the carbs, however the problem you have now could be either ignition or carbs?

But do not dispair this is not a difficult engine to sort out and simply needs a rational approach and everything can be sorted.

Firstly remove the airfilters that will resolve that issue.

Next set the timing up correctly, if you can not do this yourself go to a local MGCC meeting and ask if someone could show you how to do it (you help them )

Now you should be back to square one and hopefully the same individual can set up your carbs with you or test what is wrong.

I do not want to criticise your mechanic but finding a fault with an engine is NOT a guessing game, anyone worth their salt can do specific test and tell you what the problem is! Find someone who can do this!
Robert (Bob) Midget Turbo

Excellent advise Bob.

I have always maintained my cars before, but have never had twin carbs and the associated problem of balancing them. I have never worried about twidling the distributor or tuning the carb before, but have lost all cofidence now there are two carbs to set.As you say, I just need someone to show me then I will be OK. I do feel a bit of a plonker to be honest and should be able to do this myself.
J Mee

J - you drove it down from Wales to Cornwall right? Where did it start to go so wrong, coz I thought you'd had a good run (bar running out of fuel .....)

If your first problem was with the carbs, then THIS problem is also probably them too - especially if the mechanic isn't so sure what he is doing. Have a look for a good MG garage, that way, you can go along and have a long chat with them, they'll look at the engine as a whole, and will show you what to do so that you can do the basics yourself.

I would advise you to take off the electronic gizmo, get the engine running really well on it's own - get used to it - THEN make changes to make it more fancy. Old fashioned perhaps - but, the other rule around here is KISS ...... for good reason :)

The Burlen web site has a wealth of information that is really helpful.

If you follow their instructions carefully you will know that you have set the carbs up right. Then drive the car to see how it feels before dealing with anything else. Just be methodical.

As Bob says, only ever attempt to deal with one thing at a time!
Guy Weller

x2 Bob!

Sort one thing at a time!

I always sort out the igntion first then approach the fuel...if your points were replaced by an electronic module, the timing usually has to be re-adjusted. The replacement module does not always have the same firing spot as the point set.

This happened to me last summer when I replaced my points with a pertronix module...the timing was way off (retarted) & it barely ran & backfired under load until I re-set the dynamic timing.

Good luck, hope that helps...and yes, your mechanic may be suspect!

Dave :)
Dave Rhine ('78 1500)

Don't be spooked by twin carbs!

The only reason they make an engine difficult to tune is that people, having heard this, assume a problem is with the carbs and start fiddling with them to "tune" the engine when all along the problem is alomost always somehwhere else. Having thus made no improvement, they then tell the next person "It's right! Twin carbs ARE hard to tune!"

Follow the very good advice from others above: one thing at a time and ignition first is absolutely vital. (As it is a new (to you) car, you might also like to check the compressions if this wasn't done prior to purchase so you can confirm there is no issue there, and to check there are no air leaks on the inlet tract - in particular, the A series manifold gasket is very thin above and below the inlet ports.)

Then last of all, set the carbs. Having first checked the set-up of the jet needles (shoulder flush with piston, and it doesn't jam in the jet when the piston is lifted a little then dropped onto its seat) and that there is oil in the dampers), there are 4 simple steps:

1. With the air filters removed, adjust the idle screws to get the intake noise of both carbs the same at the desired idle speed. (There are varying degrees of sophistication for doing this, but any difference not discernable by ear won't be the cause of your problem.)

2. Adjust (if necessary) the throttle linkage so that both throttles move at the same time. (Check that the linkages are left tight enough so that there is no slip allowing one throttle to remain fully or partly closed)

3. Set the mixture on each carb.
For a car of unknown history such as this (which may or may not have had all manner of fiddlers in the past), start by getting an approximate setting: with the dashpot removed screw the nut up until the jet is flush with the base of the surrounding intake passage, then screw it down 2 complete turns (12 flats of the nut). (Obviously, do this for both carbs).
Refine this by screwing the adjustment nut up and down to get best idle on the front carb, repeat on the rear. For final mixture adjustment, the piston lifting method can be used: when the misture is correct, there should be no change in idle speed if the piston is lifted a mm or 2. If the engine slows, it is lean, if it speeds up it is rich.

4. A final step needed if any of the settings were found to be a long way out is to repeat 1,2,3 above as there can be an interaction between the throttle balance and mixture. In the unlikely event of finding things are a long way out on the second time through (which can happen if carbs are badly worn) go through the loop again.

Once set up, good condition carbs will need only minimal adjustment, if any, at subsequent tune-ups for quite some time.

If the carbs have bad wear (such as sloppy throttle spindles, worn needle valves, worn jet and/or needle) expect only limted results in terms of getting a clean idle and the mixture can be hard to set precisely. However, even with worn carbs following the above procedure will get the engine to run well under full load.

(These comments are not intended as a comprehensive tune up guide - manuals do that - but should be enough to get you familiar and comfortable with your twin carb engine given your previous experience of maintenance)

Paul Walbran

I was in your position only a short time ago. Dont be afraid as once you get into it, you'll find it's not as complicated as it seems. And you will get a great feeling of satisfaction when you sort it. You have had good advice by the others.
I would recommend you invest in a timing light and a carb-balancer. I also bought a colour tune but I can't get on with it.
The guys on this site will I am sure talk you through it. I just wanted to encourage you - my car is running really well now and if a plonker like me can do it, anyone can!
Graham M V

Hi Graham

What do you find about the colour tune? Just interested as I keep trying to find something for excess laziness ... :)

it wouldnt be something as simple as when you ran the car out of petrol on the way home it picked up abit of crap from the tank (mg tanks are supplied new with added bits and rust inside) and has blocked the pipe or carb would it.has it got an inline fuel filter?if so replace it or clean it.sometimes its best to start simple and work up. and change the filters if there in anyway faulty.there basicly the cars lungs so need to be in good nick. and dont get angry. if theres one thing you really need to own a classic mg its ALOT of patience.
roy j

>>> .if your points were replaced by an electronic module, the timing usually has to be re-adjusted. <<<

Yeah, what HE said. I was going to make the same comment - when I replaced my points and condenser with a PerTronix, the timing was way off and I had to reset it. After that, it ran perfectly.

>>> if there's one thing you really need to own a classic mg its A LOT of patience. <<<

Not to mention a good sense of humor!

Gryf Ketcherside

x2 Gryf!

Dave ;)
Dave Rhine ('78 1500)

Excuse my ignorance, but if the timing needs adjusting (which it sounds like to me - even if Mr mechanic reckons it's carbs) how do you do it? Presumably if it needs to be changed it will be different to standard settings, so how do you know where's right?
I have never owned a strobe and have only had single carb cars (before the rash of newer ones, diesels and fuel injected)and I set them up by adjusting the distributor till I got the best result by ear and the carb by the book.
J Mee

Also, you MUST sort the ignition first, you can diddle around with the carbs all you want, but if the ignition is subpar, you'll just go around in circles & get very frustrated!

Good Luck!

Dave :)
Dave Rhine ('78 1500)

When the cars were new, static timing was quite satisfactory as the distributor would still have been performing as designed. However, at this age distributors have worn and so can vary from the original spec by significant, even major, amounts.
(I have described this here: )

The problem with adjusting the distributor for best idle is that the high manifold vacuum conditions at idle make it respond well to a lot of advance but until the mid '70's MG's had no vacuum advance at idle. Rotating the distributor on such cars to fastest idle makes up for that, but ends up with way too much advance everywhere else.

Because of both these factors it will be difficult to get your ignition set up properly without a strobe.

However, if you are anable to buy/borrow/steal one, for progressing diagnosis of your current situation static timing should at least put you in the ball park.
Obviously, with the electronic set up you can't use methods which detect when the points open. The way to do it is to
1. Mark the current distributor position, marking both distributor to clamp and clamp to block. This will allow you to reference whether the timeing was out, and if so by how much. 1mm at the distributor base is 6 deg on the crank so make sure the marks are clear!
2. set the crankshaft to the required static timing point (7 deg for 1275, 5 deg for 1098) with the rotor pointing towards no 1 plug lead
3. fit the distribuotr cap, remove no 1 plug lead and fit a spare spark plug to it (with the body of the plug suitably grounded to the engine)
4. Find the approximate position for the distribuor by rotating it fairly rapidly clockwise until a spark apears at the spare plug. (You may have to rotate the distributor anticlockwise 20 or 30 deg first before doing so in order to ensure the timed position is covered on the clockwise sweep)
5. Having noted the approximate position, refine the process by using a smaller angle of sweep centred on the approximate position and moving the distributor as slowly as it is possible to do yet still get a spark. Tighten the distribuor clamp.

This process may end up with a degree or two of extra advance. In engines with timing marks visible from the top, I would then check by rotating the crank and seeing what the pointers read when the spark appeared. However, this is a luxury for engines which still have the timing marks underneath! In any event, the right maximum advance usually results in more advance at static on a worn distributor.

Static setting this way should get the timing into the range where it will run reasonably well (unless the distributor advance is seized ot totally flogged) and from there you can road test to where it feels best (keep noting what the changes are so they can be reversed if you need too).

However, for best results if you are planning to maintain your car in the long term (as it sonds you are perfectly capable of doing) a strobe will be essential. It costs less than even one bodged "professional" tune-up!

Paul Walbran

I'm going to buy a strobe - just looked on ebay and they are pretty cheap. So I'm going to have to learn how to use it and how to set up the carbs. It seems wrong that I have looked after my own bikes and cars all my life and then panic when confronted with two carbs!
With this electronic trigger in place is it easy to time with the strobe?

THANKS, by the way for your answers and patience with a numpty!
J Mee

There are some pretty crappy cheap timing lights about. I messed with a couple over the years before getting a second-hand Snap-on tools one which was just so much better and nicer to use. Something like this e-bay one:

140415606595 -in case the link doesn't work.

There are a lot of them available.

And ... I don't believe you are a"numpty" at all. Just maybe a slight lack of confidence because of the rumours that twin SUs are difficult to adjust - which just ain't true! If you have looked after your own cars and bikes for years then this is no different!

Guy Weller

Numptys are the ones who DON'T ask for help/advice. Your courage will see you through.
JM Morris


That ebay listing has been removed, apparently!
Dave O'Neill 2

No its still there. Try the number rather than the link.
For some reason that I don't understand the Tiny URL links I do for e-bay sites often seem to abort. Maybe e-bay don't like them! ?

I wasn't necessarily recommending that particular auction - it was a random choice - but there are lots of them on there at present.
Guy Weller

The only reason I cant get on with colourtune is that I cant see the colour of the flame change properly. Maybe its my eyes but have tried several times and just cant seem to get on with it. Others may have different views.
But just to prove I havent got an angle against gunson, I would recommend the carbalancer to J. Really easy to use.
Graham M V

Colourtunes will get you in the ballpark at idle, especially if you have two (front and rear spark plug). I never found them useful at any other rpm.
JM Morris

J Mee

If you are using a strobe, set the static in much the same way as I indicated, but instead of using a spk plug and watching for the spark, attach the strobe in the usual way and hold the trigger in while you move the distributor. The light should flash when the distributor fires the current to the plug.

Once you have set static, start the car and set on full advance - 30 deg at 4500RPM will get you in the right place. Get a strobe light with the advance adjustment dial on the back of it - much easier to work with.

If your timing marks are underneath the car, bring cranks to TDC on those marks then, from the top in a position you can see it easily, paint a new mark on the pulley and one opposite on the timing cover - much easier to work with!
Paul Walbran

If you're looking for a pro in Cornwall to set your car up, Tim Kelly MG in St. Agnes is excellent. He'll do you a good job.

If you want some amateur help, drop me a line at mhharrisATtalktalkDOTnet. It really shouldn't take more than a hour or two, and once you've been shown once it'll be easy as pie next time (if it ever needs doing again).


Once you have your carbs sorted, just leave them alone.. These carbs do vary slighty from day to day, atmospheric pressure, air temperature, engine temperature, weight of shoe etc, just top up the dampers from time to time.
I had this advice at an SU depot, who tuned the twin carbs on my little Riley 1.5 back in 1962.
In other words, to use the modern idiom: if it aint broke, don't fix it!
AG Martin

Or do as I do...if it ain't broke, fix it until it is!
Dave Rhine ('78 1500)

This will be my last question on this thread, as I am in serious danger of boring you all witless!
Having read that my car might need re timing due to the electronic module AND due to the fact that my mechanic chap still owed me satisfaction, I arranged to take Widget to him this morning.
Starting with choke went OK, and driving off down the road again went fine till I released the choke. Then it was cough, bang, stutter etc etc again. SO, I pulled the choke out a little and all was well again until I came to slow down for traffic and the revs were too high (as they would be with choke) so I released the choke and it died again (cough, splutter,bang).

Now this indicates to me that there is something wrong with the mixture YES/NO?

The car ran fine with a little choke.

The mechanic (who is rated by the whole village? and is a nice bloke(don't want to upset village life!)) told me that it could be worn carbs as he set them up correctly and that I should put some air filters on that work before he tries anything else. He reckons that air is leaking along the "shaft"? possibly and weakening off the mixture.

I am all fired up to have a go myself now, but want to let him have a final go first, as small village life can get awkward if feelings are hurt - and I have paid him to sort it.
Having read about carbs running without filters perfectly well I am now unsure what to do for the best.

COULD WORN CARBS BE THE FAULT and WOULD REPLACING THE FILTERS HELP? (I can see that they would enrich the mixture a bit, wouldn't they?)
J Mee

Hi J M
You will not bore me cos I love talking Spridgets and mending them! and have done for almost 40 years :)

OK you are correct the problem is with your mixture, as you rightly observe when you enrich the mixture with choke then the engine runs fine.

The first thing that bothers me is your mechanic claims he has set the carbs up correctly, if so why does it not run?

If they are faulty why does he not say "can not set the carbs up mate cos they are f***ed! or whatever!

Naturally air filters would improve things slightly but not by that much

Unfortunately the engine needs to run before the carbs can be correctly tuned. However even with really bad carbs the engine would run better than you are describing.

What can be wrong is an air leak around the manifold it is worth checking.

I think you should have a go yourself, if the good people here instruct you do you feel capable?
Bob Turbo Midget England

I'm sure he's a very nice man - who talks alot of twaddle :)

The mixture is wrong and it's set up incorrectly - and yes, air filters may or may not be bad - but, shouldn't HE be doing that for you, and not refusing to do any more work until you've done it ...?!

Don't worry about it - we've all been there :)

Oh bum! I knew you were going to say that!
I am one of the village postmen and I deliver post to this chap and always stop for a chat. I wish I hadn't asked him to do it, but everyone in the village recomended him. He has got a Westfield that runs crap too ha ha ha!

Oh well I'll have a go and tell him I had a fiddle and (perhaps) amazingly it works!! I'll also look for air leaks - are they easy to spot?
J Mee

LOL ah - still, you could ask him if he could really check out the carbs and tell you if he thinks they need replaced ...? However, if he's got a bad running Westfield ...!

In all of this messing about have the air filters been removed and replaced? They may have been fitted wrongly and are blocking the extra breather holes in the carb flange - as was discussed on a recent thread.

Assuming this is not the case, if you can get it running on tick-over try then spraying some WD40 onto the ends of the throttle butterfly shaft will indicate if they are worn as the engine speed would change. (These are the shafts that your mechanic is referring to when he says they may be worn.) But if they are worn here, unless they are very bad indeed, they would not prevent you from getting a reasonably well running engine. Not perfect, but acceptable to most!

Guy Weller

Have we verified yet that the ignition is in proper working order?

I agree, you may have carb problems, but before they can be set correctly, the ignition has to be working correctly.

It's been my experience that worn throttle shafts will cause fluctuating idle problems, but not the problems you're describing.

And keep posting, we all love it, that's the reason we keep coming back to this forun!

Dave :)
Dave Rhine ('78 1500)

If I can add my 2p - although I am somewhat of a novice compared to many on this forum. The air filters are designed to do just one thing, filter the air to prevent rubbish getting in to the carbs. In doing that, they reduce air flow to the carbs and so, rich the mixture. From what you are saying, you can only get the car to run when you richen it using the choke, so I cant see the filter is the problem.
But I assume your mechanic has seen something he doesn't like with the filters, so why not just take them off and set up the car without them? I assume you wont be driving through sand storms? It will at least eliminate one thing as there is no reason on earth why the car shouldn't run well without them.
Graham M V


Totally agree & why not just replace the filters, it's proper maintenance anyway!
Dave Rhine ('78 1500)

Worn shafts do indeed leak air, owever by good fate the extra air is usually approximately cancelled out at idle by more wear at the thick end of the jet needle then further down the needle, due to contact with the jet at some time in its life.

If the needles only are replaced and the idle mixture reset, then the engine will indeed run lean everywhere else. However, the amount usually just causes hunting at lower speed (30-40 mph) cruise conditions.

I suspect there is an air leak as Bob has said. As I noted before, the head to manifold gasket is very thin above and below the inlet ports and failure there is a common cause of air leaks.

Another cause can be a crack in the heat shield which extends into the join between carb spacer block and manifold.

For good practice, I would still check the ignition timing was correct, as I have had similar syptoms of running right under choke(though not as bad as it sounds yours are) when ignition timing has been severely retarded.
Paul Walbran

OK - I think it's time for you to have a systematic run through of your timing/fuel supply - well - whole thing really! If I remember correctly, you've not long had the car, and so it's always a good ideais to check everything. I'm not saying the previous owner was good/bad or indifferent, but, it's always a good thing to do.

If you're not feeling confident, I think that someone did suggest a garage somewhere in Cornwall - is it terribly far away from you?

Change everything that needs to be changed, don't forget to have a jolly good clear out of fuel in the lines (as you did run out of petrol it is possible that some gunk was picked up, or if the car had been sat around for awhile, then I don't care what others say, the fuel is rubbish and does cause problems!)

At the end of that - I'm not saying that the car will run perfectly, but, at least you'll have ruled out the obvious and easy problems - then, as Sherlock Holmes said - whatever is left, however improbable, must be the truth! OK - so, it's a total misquote, but, you get the idea!!!!!

Don't worry about posting - we've all been there, the only way to learn is to ask - and we've all made the most stupid mistakes, so don't get embarrassed to ask :)

Rach - who's current biggest gaff was doing a run on an autotest with the handbrake on - guess that's the next thing to be replaced...!!!

It sounds to me like your mechanic has lost his way. If he can't do anything more for you take it back and have a go - it sounds like you couldn't mess it up worse than he already has.

2 years ago I was a complete novice at this, and was shown how to do it by my dad's neighbour who owned two MGBs. When I put my car back on the road just over a year ago, I asked the guy who MOT'd it to balance the carbs for me, as I thought he'd do a better job than I had. He did it for me, but the car ran worse than when I'd given it to him; so I started again and got it running well again. It's a dying art, I think!

Sounds like you need to go back to the start -

Take the tops off the carb and then do up the jet adjusting nut until the jet is level with the deck (the end of a steel rule is ideal for finding that spot). Back it out by 2 turns / 12 flats and that will get you close enough for the engine to run. Put the dashpot back on, top up the damper.

You can then start the engine and go on to the balancing procedure as described by Paul above.

And my offer above stands if you'd like a hand doing it...


When it rains!!!!!!!!!!!!!

I thought I would have a fiddle today, having started to put a new hood on yesterday (waiting for some stainless screws to arrive) which seems pretty straight forward, anyway, the engine had a dribble from the front so I thought I would sort it before I started to look at the carbs.
Close examination seemed to suggest a leaky gasket on the thermostat housing - duly replaced but there was still water spraying from the fan and belt and it seemed to be worse.
It seems like it is coming from below - maybe the water pump, but while I was looking the temperature went sky high so I left it.

Is it likely to be a gasket, do you think?( I hope it's nothing nasty)
I'm not sure where it's coming from yet as I can't see for water being flicked up by the fan.
I will take the belt off tomorrow and see if I can see better.
J Mee

(If yours has one) you could also look at the bypass hose and its clips (below thermostat housing)

One of the main reasons I use 4-LIFE engine coolant is that it is great at highlighting the source of leaks, you follow the spray pattern or residual droplets CSI fashion

4-LIFE has helped me to prevent problems exculating and has a 10 year life but whenever I've used it in my cars it has had to be emptied back out just weeks or months later hence for me it's more like 4-now
Nigel Atkins

Mark, did you get my email?
J Mee

I'd go for the bypass hose too, the most common source of leaks in that area. There is a bellows type hose which can be manoeuvred into place without removing the head. You may also find that the fittings which it clamps to (part no 12A2075) are rusted and need replacing. (Unfortunately this involves removing the head. If you do have to remove the head, use a piece of heater hose for the bypass as it is heavier in the walls and longer lasting).

The second most likely failure I would put down to the water pump, especially if the car was parked up for a while.

These leaks can ver very hard to distinguish one from the other at times, so you will need to have a good close look.

There is always a first time, but I have yet to come across a gasket failure as a cause of a leak in that area. (or maybe the cars I've seen were just lucky)
Leaks at the thermostat housing (which you have checked) tend to be down to corrosion at the gasket face allowing the coolant to track to one of the stud holes.

Paul Walbran

J - can you get in contact with the bloke you bought this from - hose away any bs - and ask him EXACTLY what work has been done - how many miles it's done in the past year and see if he's got any proof of any of this? Seems to me you need a bit more history on it.....

The car has only done 13000 in the last 20 years and then only in the summer, in dry weather and with the roof down for short pootles.
At first I thought this was good and was the reason I bought the car, but I am beginning to think that a regularly used car would have been a better buy.
I am sure there are issues that I have found that the p.o. did not mention and was perfectly aware of.
The car has had a lot of money spent on it over the years (mainly when it was restored in 1990) with lots of new parts but the guy obviously didn't need to fix some of the faults that developed lately with the mileage he was doing.
I suppose I should have been a bit more savvy, I knew there was a small water leak but was sure it was from the thermostat housing WRONG! I knew it was running a little poorly but it was fine with a touch of choke - took it to someone I thought I could trust to fix it -WRONG! I knew the hood had seen better days and bought a new one and am fitting it myself - RIGHT!
I am half way through restoring a basket case Moto Guzzi and with very limited finances perhaps I shouldn't have taken on the midget as well - but hey, you're only old once!
I will fix the water leak before I play with the carbs myself.
J Mee

Ultra low milage and intermitent use cars just stored up the problems

Regular use will start to find and eliminate the problems (usually by replacing/repairing/refurbing parts and components)

Two years of regular use should get you passed the stored problems

A lot of problems will not stop you using or even enjoying the car and can go on the to-do-list but where you can get the problems sorted or they will spoil your enjoyment and create further problems - most things on Spridgets are relatively very inexpensive

Best thing next to regular use is FULL (see owners Handbook) regular servicing

Oh and try to avoid those that don't know what they're doing or are happy to do a poor job for your good money (wish I could)

Paying out more at the start will most often save you more money in the medium and long term
Nigel Atkins

hmmmmm - kinda figures - and kinda double what Nigel says - and go and see Mark :)!

HOWEVER - it WILL get better, and you will have fun, and you will learn loads in the meantime ...!

Sorry meant to say a lot of the stored problems will be minor and will get ironed out over the two years of regular use and full servicing

You'll find as you're able to increase your use after the first lot of finding faults that the faults and problems deminish inverse to your regular use (does that read right and make sense(?))
Nigel Atkins

This thread was discussed between 11/06/2010 and 18/06/2010

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