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MG Midget and Sprite Technical - £500 Spent and rough still idle??!!


Just got my 1275 midget back from a specialist MG garage in surrey, no names as they have not had a chance to speak with me about it yet.

I had new Plugs. Leads, Magtronic Ignition, K&N Pans and Richer needle Carb balance a general tune up valve adjustment etc etc.

Not moaning too much about the cost as i expected around 400 ish so thats not the issue.

The issue is it went in for rough ideling and poor starting and still has the rough idle.

When i left the garage all seemed well and i was quite impressed with it being more responsive its a 40 min journey back home about 25 mins in doing an average of 50 i came to a junction and reves did not fall back down i fiddled with the accllerator peddle and it then stalled as the revs dropped too low seemed like the cable was sticking on the acclerator so sorted that but now rough idle AGAIN

Got home and its running all over the place, checked leads and connections all seemed fine but i did notice the coil was very hot, could it be this? any other info greatly received as long as its not over technical as thats why i trusted it to a specialist MG garage :-(
mgdan2

A worn spindle shaft can cause this idle, spray some grease on the bushes and listen, or feel if there is some radial movement.
Flip
Flip Brühl 948 frog 59

Check that the butterflies in the carbs don't have the over-run valves in them!! They fitted them for a short period, until it was discovered that they stick and cause the idle to go mad. If you've got them, solder them shut.
D le Versha

The moral of the story is do it yourself. The Midget is not that difficult to maintain (despite the problems I have struggled with) and the basic tuning tasks are not that difficult.
As mentioned above, check the throttle spindles. If they are leaking the idle will be rough. Also check the mixture, if it has been set too rich it won't idle too well but it sounds to me like an air leak somewhere.

Dave
D Brown

Go back let them fix it!

Non of the added parts automaticly fix rough idling.
A good tune will

Remeber with the basic setup of carbs and points it should be able to run smooth and start easy.
Only when an engine has been modified do you need to change some of these parts to get it running properly
Onno Könemann

I had a similar problem and following advice from this board, I directed a jet of propane gas (from an unlit blow-torch) around the back of the carbs and manifold and by hearing an increase of engine speed at a particular location,identified an air in-leak. It turned out to be a cracked inlet manifold.
Do you know, this is the second time this has happened to me in 33 years of vehicle ownership - its just not good enough !
Anyway, done a temp. fix with Araldite while I keep a lookout on E-bay.
M J Chapman

After a tip from this site, I sprayed the ends of the throttle spindles on my 1275 with WD40 and the engine idling, To my amazement on one carb. the engine nearly died, on the other side it did die.
I glued a couple of rubber cups over each spindle end, and the slow running has been great ever since, after adjustment of course.

Dave
Dave Barrow

Thanks all, im sorry to say even though i know this is the tech page which is why i asked for a non tech description but i guess you guys know one end of a carb from the other..lol... im NOT at all technicaly minded :-( i can adjust the carb screws and check leads etc but thats about my limit, hense spending the 500!

I did lube up the throttle which was sticking and this helped slightly, its now not too bad but im still not happy after paying for it to be tuned along with the pans,leads plugs and magtronic ignition.

It is far more responsive and runs and starts well its now just slightly rough idle after adjusting the carb screws which as i said is about my limit.

The garage did balance the carbs and have suposidly tuned it fully after adding all the new parts but im not happy and WONT be going back there especially as they wont return my call or answer emails i sent.

Anyone on here know of A GOOD garage in the south London surrey area???

Im still not naming the MG Spcialist despite them not returning my call or email but its fairly easy to guess as they are a surrey based mg specialist.

mgdan2

mgdan

Learn to do some of this work for yourself.

Just consider the labor you're paying someone else...that would buy ALOT OF PARTS!

These little cars aren't that difficult to work on & you have this forum & others to help you out.

Just a thought...
Dave Rhine ('78 1500)

Hi There, You mention that your coil is getting hot. This is not normal in my experiance and could be that a) It is not compatible with your new electronic ignition b) They wired up your new ignition incorrectly or c) Most likely it is arcing out inside which is causing it to over heat and also giving a weak spark which might be the casue of your erractic idle. Likely it will fail shortly so I would buy a replacement.

My money would be on an air leak on your inlet manifold or carburetors though especially on teh throttle butteflies where the spindles exit the carbs either side. Get yourself a length of small bore tubing stick on end into your ear and feel about with the other end all over your inlet side, carbs and inlet manifold.

With the engine running of cause, if you suddenly hear a load of hissing then youve found your leak, unless your on the air filter :-)

Ben Brown

You don't have a performance cam by any chance? That can cause a lumpy idle, with performance smoothing out as revs rise.

Cheers,

-:G:-
Gryf Ketcherside

Im with BEN...

Can you give use anymore details on the heated coil...are the wires attached to the coil also hot, what kind of temps are we talking about.

To ADD to Bens thoughts... have you inserted any screws into the fire wall recently, maybe around the radio concel, If you created a double ground, by sticking a screw into an ignition wire or wiring harness, (and its easy to do, esp if your good kissing buddies With Mr. Murphy) Sometimes you can just Pinch a wire and break thur the insulation with continual metal contact and have NO JOY...

I did that on my work truck several years ago...Jez what a night mare that was...

anyway Id grab hold of the wires coming out of the coil after its been run for 20 - 30 minutes and see if they are hot...If they are, you may be able to scratch carb issues off the list.

Prop
Prop

Gryf,
i was thinking exactly the same.
Brad 1380

Ben/Prop Thanks will check wires also for heat, when i say the coil is hot i mead HOT enough so you couldnt hold it! i think this is going to be the problem. ive loocked at the wire and as far as i can tell they are correctly wired though.

Is there an uprated coil i can buy or do i but a standard 1275 one?? and at least something i can do myself..lol Gryf/Brad no its a standard cam.

Idiot question but are the throttle butterflies the pin like parts underneath each carb? i had a look round the carbs and if it is these they can twist and seem to push up which then drops the revs to a stall??

I really sorry guys but you are talking to a real novice here! lol
mgdan2

The std cam can give simular problems if timed incorrectly.
Anny engine work done?

The throtle butterflys are in the carb
they are the part that is inside the carb connected to the throtleshaft.
They open to let a certain ammount of mixture through
Onno Könemann

Checked coil wires after a run today they are not gettind hot just the coil.

Located the mixture nuts (see ive started to learn!)and tried adjusting these a little but still cant get it to run smoothly.

Also noticed it runs on sometimes after ignition switched off. checked the jets (oil level ok) and needles(they were replaced by richer ones by the garage)

Im just going to have to get someone else to have a look at it :-( more expense...lol

Im not going to attempt deep surgery on the carbs etc as that is definately beyond me at the mo.

mgdan2

I would pop a new coil on before fiddling with anything.

Which fuel are you using? I've cured a few ill's (running on and such like) with a tank of Shell V power
R Fowler

MG DAN.
May I suggest that you stop fiddling with it and actually return to where you spent $500. Your fiddling may have cost you any warranty they would offer.
Sandy
SANDY SANDERS

Certianly a head scratcher...on one hand it sounds really basic issues, on the other...Its basic enough Im sure the shop would have seen the issues and fixed them.

I think you might have 2 seprate issues...

1. a bad coil ??? and 2nd is everything else... LOL hahah

sorry about that, what I mean is you mentioned several more things that can go in 1 of several directions

you said you pushed the pin under the carb and it stalled...thats a sign its running to lean, I wont get into the pin you pushed, but sufice, if you push it and it stalls its lean, if you push it and speeds up its rich, if you push it and it slows down then recovers its correct...but that is dependant on weather the jet/needle are centered properly

Next you mentioned run on or desieling

that can be one of several things...

1st check your timing is correct, check the idle speed is around 1000 rpm, (Some times this happens because its to rich but i doulbt in your case) and last ALOT of carbon build up in the combustion chamber


The direction I would persue

Take it to a classic british machanic...

NOT a modern day car shop, the tech is to old for these newer car guys to understand, case in point you said the shop installed new richer needles, but do they know how to center them properly, if not, you can run lean if thats not done correctly, did they use the 20/50W oil in the carb dash pots, or just whatever was lying around in the shop shelving...agian a big issue ... this is why learning to do it ALL yourself is such a big game changer and why we have all made the investment to learning how to do it ourself,you just dont know the experiance level of a guy working in a shop that you never met before, even tho the guy at the dervice desk says "sure we can screw up (doh sorry, fix anything)"

If you do it yourself ... You need a methodical method of approach.
Personaly for me, Id find out why you have a super HOT coil and cold wires that cant be touch after 20 minutes of operation then procede to the the issue of run on/diealing, check the timing and idle speed, once those check out or resolved then see if the carbs are still lean, ect ect.

what temputure is the engine running after 20 minutes, does it want to over heat vary often? what does the exhaust look like is it vary black at various throttle positions
Prop



Like Sandy says.... (BTW Sandy thats NOT $500...its MORE then $750 in USA currency)

Take it back, Plus Id question the level of experiance and level of knowledge that the actual hands on mechanic has. For that kind of money you have paid for the right to do so, and to have a truthful ansewer. So check his referance, anyone can say they belong to a MG car club.

If he owns these and drives them, his friends do as well and he belongs to a classic british car club... then great its probably just a minor hickup the guy can easily correct...esp for $500 IN YOUR MONEY ($750 our USA Money)

BUT if the hands-on mechanic just read a 15 year old road and track magizine artical in the bathroom while sitting on the johnny about old SU carbs and is relying on his wrench turning skills to take the carbs apart, stick new "Richer" needles/jets in and put it back togather, Plus adjust correctly (they did replace the jets also didnt they) then Id say you have some serious Re-negoating to do with the guy that owns the key to the cash drawer.

Prop
Prop

Prop..
I agree with you on the currency conversion. I was just too lazy to look up and use the proper sign for the British pound.
Sandy
SANDY SANDERS

Sandy

Im not sure about you, But im in the wrong business... I cant grasp the concept of $750 for a tune up with the addition of 2 richer needles (and maybe not a jet) and some air filters...I know it all adds up, But I can still remeber a loaf of bread only costing $1.25, and a 1/2 gallon of milk for $2.00 and that was just week.


pertronix $90
richer needles $10 each = $20
K&N filters $125
spark plugs $15 for NGK silver

$250 in parts + 3 shop hours = $150 per hour, plus $50 in taxes and fees

wow, I knew there was a reason I do all the work myself...until now, I almost forgot why.

Prop
Prop

ok - I've got 5 quid here that says its an air in-leak and the "Specialist MG Garage" has put richer needles in/adjusted the carbs to run richer and that's what's causing the running on.
Take a couple of spark plugs out and I bet they're all sooty !
M J Chapman

MJ

Points HAVE to be given that they didnt get the K&N air filters on corretly, How many times have we seen that? BUT Im to much of a coward to take you up, I tend to only wager on things where I have at least a 7% chance of winning

Im still "leaning" towards the new needle and seat arnt adjusted properly and the coil has seen better days...a 2 part-er

Prop

Hey this is a great thread all over the shop :-)

Definately buy a new coil and try that it should not get hot just buy a standard one they are not expensive, but get the right one for your car.

Just to clarify on those little spring loaded pins under the carbs.

With the car idling and fully warmed up and choke off

Push one pin fully up sharply -

a) Car stalls out straight away - too weak lower the jet

b) Revs rise and stay high - too rich screw the jet up a bit

c) Revs rise for a second then drop away quickly car will run lumpy and may stall after a few seconds - Mixture just right.

Then repeat on the other carb.

A word of warning this behavour only happens when everything else is set up fairly well. i.e. if the carbs are out of balance you wont get such clear results, knackered coil, ignition timing way off ...

So in short if this test is not conclusive then likley you have problems elsewhere once you have fixed that come back to this one.

My money is still on an air leak and the garage fitted richer needels to try and fix it. The throttle spindle is the shaft that is connected to the throttle linkage. If you pull on your accelerator cable then these are the parts that rotate :-)

Ben Brown

well thats part of it

you want to release the pin quickly and listen for a clank as the carb piston hits the bridge and the jet is in the fully up postion

if can only get a clank when the jet is fully lowered then the needle needs re-centering

Here is an excellent online artical for tuning the SU carbs...(Look to step 4..under the adjusting mixture heading about 1/2 way down) about using the little lifting pins...there are somethings that have to happen 1st before you do the lifting pin test.

agian a great artical thats easy to understand and replicate...Id say copy it off on a printer read it several times make a copy of the moss blow up dia gram that list all the parts ... take the 2 pages with you and some tools and with in an 1-2 hours you will be singing how great i are in the C octive

http://www.nicoclub.com/archives/2-write-ups-on-tuning-su-carbs.html

http://mossmotors.com/Shop/ViewProducts.aspx?PlateIndexID=29282#A

Prop
Prop

FINALLY! getting somewhere... had a mate look at the issue.

1) The MG 'Specialist' garage should have changed my coil to a 12 volt when they changed the Magetronic ignition over.

2) Not a manilod leak

waiting for coil and he will then tune it correctly.

Even i new the coil was too hot and its pretty obvious as the electronic ignition works on a steady 12 volts that a 9 volt coil is going to overheat... good job Mg Specialists of Surrey!
mgdan2

you didnt have a 12v coil? what did you have? How many volts?


make sure you research your system a bit, some systems use a ???? (drawing a blank) resistor, a bias, electrical filter ...its a piece of fiber clay that the positive leads hook into and it steps down the current ...

someone help me out please whats it called
Prop

Dan - might I suggest that you join ONE (or more!) of the clubs and go to the meetings (free if MASC/MGCC) and speak to some of the people there - not only will they be able to pick up a problem at 100 miles, but, if it's not Lincolnshire, they'll probably be able to do a better job than you - and, as you've said you can't do it yourself, they will probably take the time to teach you.

The engine is pretty simple to work out really, and the 1275 does have alot of room in which to work.

Plus, it's a great way to get out and meet people and do all sorts of things and have fun :)
rachmacb

Surrey Section Midget & Sprite Club meet monthly at the Blue Ball, Walton on The Hill, Surrey. on 3rd tuesday from 1900hrs.
Next 21st Sept.
www.midgetandspriteclub.co.uk
A Anstead

Prop, ballast resistor is what you are looking for, droped the output to 9 volts is what my mate was saying hense the need to change to coil

Thanks all for info on clubs will be joining soon :-)
mgdan2

Yipee sorted! completely different car now... runs like a dream :-) thanks to Ben Prop and anyone else who suggested the wrong coil... now has the correct coil for the magnetronic ignition and re tuned.

Shame on the MG specialist garage in surrey for not picking this up.
mgdan2

Congrats MGdan2,

Its great when a plan comes togather, Now please spend some time reading Danial stapleton, Vizard, and the haynes manual, and attend some local club events, otherwise your only enjoying a small part of what the Midget experiance is about

Prop
Prop

This thread was discussed between 02/09/2010 and 14/09/2010

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