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MG Midget and Sprite Technical - Rough running

Hey everyone, this is my first time on here. I'm attempting to get my 1974 Midge ready for spring, however, I'm having some issues getting it to run right. It seems that at nearly all RPMs it runs very rough. It has a brand new weber downdraft setup from pierce manifolds, new rotor and cap, new wires and plugs, new properly gapped points, and a new coil. Only other modification overall is a new muffler from a Harley soft tail. :p
The head has been off of it as well over winter - in case it could be something to do with the valves. He car has not been run in years so I'm trying to get it back on the road.
Any thoughts or info would be much appreciated.
-tim
TS Sherwood

It seems to have had a lot of new stuff for whatever reasons you believed however you have not suggested if you have set up the timing correctly or if you have set up the carb?
Robert (Bob) Midget Turbo

do a compression check?
robnrrugby

Timing is next on my list, I have not ruled it out yet. I have not set it with a timing gun, however, I have loosened and moved the distributor to find a "sweet spot" but had no luck, there was no point at which it was any better.
The carb is set up about as well as it can be. Hard to tune that out nicely while it isn't running well. Adjusting the carb had no effect on that. Although the vacuum advanced is disconnected, and I don't know what issues would arise from that - although for whatever reason I seemed to think that it wasn't an abnormal thing for people to have it disconnected with aftermarket carbs.

Compression check is a good idea, I hadn't thought of that.

Thanks!
-Tim
TS Sherwood

Tim,
Not sure what you mean by "rough running". How rough? Is it actually misfiring or just not pulling smoothly when driven? I think we need a bit more information!

If it is very rough, with the engine struggling to run at all are you sure that you have reconnected the plug leads in the correct firing order?

If everything is as it should be, and it is still running roughly, then your best bet would be to get it set up on a rolling road. Then at least you will know it is right.
Guy

Hi Guy,
I know, my description leaves a bit to be desired. Basically, At all RPMs it coughs. Any better yet?
Ironically, the plug lead order was what kept the previous owner from ever getting it running (that and the few ignition components listed in the first post.)
I have to imagine they must be right as it sits. It does run, it will sit there and idle (roughly). Although, I can't say it is set as low as a normal idle speed yet as the tach is not functioning.
When you hit the pedal you feel hesitation, and then at the higher RPMs it continues with it's light cough.

It sounds like it is misfiring randomly, that is the best I could put it. Although I have not a clue of whether it is actually a misfire. The "running rough" symptom going on is not a consistent sound - like a cylinder not firing is a consistent sound, or feeling. With this it is random misfiring or "coughing", random but constant in the sense that it isn't stopping - the order or timing is just random.

Thanks!
-Tim
TS Sherwood

Probably not the firing order then, although a car will run with two cylinders firing "out of sequence".
Guy

Worn out dissy ?....

or perhaps the PO tried to pull the dissy and the drive dog is off a few teeth....the fact that the PO never got it started and did alot of work.... really makes my skin tingle with a gooy ick

I think your best approach is going to be a well thoght out methodical step by step plan...and just go thur it all


Just a last simple idea ... make sure the little braided mesh wire from the engine/tranny to the body is still in place.and good shape...its next to the oil pan.

Prop
Prop

Might cosider giving the valves a look and make sure there adjusted to spec.

Prop
Prop

Worn out dissy ?....

or perhaps the PO tried to pull the dissy and the drive dog is off a few teeth....the fact that the PO never got it started and did alot of work.... really makes my skin tingle with a gooy ick

I think your best approach is going to be a well thoght out methodical step by step plan...and just go thur it all


Just a last simple idea ... make sure the little braided mesh wire from the engine/tranny to the body is still in place.and good shape...its next to the oil pan.
Prop

Tim, hi, unfortunately you can't assume because something is new that it's not faulty, new rotors and points have often in the past been of poor quality manufacture

I'm not saying that these will be at fault but it's worth checking, buy new from somewhere like - http://www.distributordoctor.com/rotor_arms.html

new HT lead being faulty we had an example just recently on the BBS

new plug being faulty - I had one very recently (it was NOS though but proved Bill right and Bob wrong on this occasion)

Also full servicing is often forgotten, things like lubing dissy cam and oiling dissy - I realise you may have already done some bits but go through a 36,000 mile service step by step (for the whole car too) and that will give you a good basis to start diagnostics

Of course it wont cover, and specialist area of, the Weber
Nigel Atkins

I would assume that being new the weber was originally specified for that engine so ought to be set up pretty close. Whilst the timing will now be a million miles away (your suggested technique is crap!) I doubt it could cause a problem as you have described hat it is not a rythmical misfire.

What condition are the plugs when inspected?
Robert (Bob) Midget Turbo

(your suggested technique is crap)

Gee Bob,

You should really try to be more direct and to the point...there seems to be alot of room for confusion in your statement.....hahaha

In a little more "direct tone" yeah your sweet spot idea of timing wouldnt be advised by many ... but that hasnt stopped myself and others from making a prayer and giving it a try...but you do need a light to be effective
Prop

The reason it is crap Prop is because it will always cause the timing to be set too far advanced. I cant be bothered to explain why except to say that when that technique is used without the vac adavance connected then the result is even worse!
Robert (Bob) Midget Turbo

I agree... and was just making fun of the tone of your comment.
Prop

Pleased about that Prop, I will now sleep at night!
Robert (Bob) Midget Turbo

This thread was discussed between 30/04/2011 and 01/05/2011

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