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MG Midget and Sprite Technical - Can rotor button be 180deg out?

ok finally have my car running. yippee! One very minor issue the HT leads are not how I thought they would be. no.1 lead is out the back of the cap and no.4 is out the front (25D). It obviously works fine like this but looks untidy with the leads crossed over. I don't think this is how they should be. I'm assuming no.1 should be at the front of the cap??

I'm sure the drive gear in the engine is in the correct spot. I've double checked that but I did rebuild the distributor a while back and was wondering if the top of the ditributor can be spun around 180 degrees and put in back to front or will it only go in one way? If it can then this would be where the problem is. I could just pull it apart to find out but didn't want to do that and find out it was correct to start with. In posting here, perhaps I'm getting a bit lazy.
Greg H

photo need I think Greg

the rotor has a locating block inside it that obviously goes into a big nick in the middle drive shaft of the dissy so if you don't locate it properly the rotor will be too high

forgive any incorrect terminology but I'm sure you'll know what I mean
Nigel Atkins

As I am sure you will know the dog key on the top of the lower drive shaft(pinion gear) is offset so that the drive shaft to the dizzy will only go in one way. But you can remove the lower shaft and rotate it around so that the whole dizzy will then turn through 180 degrees.

You need to get a long bolt or piece of studding that screws into the centre of the lower drive shaft. You then use this as a handle to ease it up out of gear mesh with the cam shaft and rotate it around - you can feel the gear teeth as they disengage and move on 2 or three teeth of the spiral pinion. You need to turn the shaft through 180 degrees by the sounds of your description.

And then you need to reset the ignition timing!

oh your looking the other end - would this help -

or is it your timing or timing marks out(?)

still think a photo might help
Nigel Atkins

Which part of Guy's advice don't you follow Nigel? :)

If the dizzy drive has been correctly fitted in Greg's engine (and that is often a difficult thing to do even for those who have done it regularly) then the drive dog on the bottom of the dizzy is 180deg out.

Greg I would follow Guy and rotate your dizzy drive through 180deg...
James B

The *easy* way, as already mentioned, is to remove the distributor drive and turn it 180 degrees. The standard air-filter mounting bolts are very useful for this.

Many Haynes manuals are incorrect when they deal with the installation of the A-series distributor drive gear, which is why they regularly end up 180 degrees out.

I always set the engine to TDC with number 1 firing - which IIRC is NOT with the timing gear dots adjacent - I look at the dissy with the rotor pointing where I want it and check the drive dog orientation. It is then a simple matter to fit the drive gear so that it aligns with the dissy.

Works every time!
Dave O'Neill2

Nigel here's a photo for you. You'll have to follow the leads to see what I mean. :)

Car runs fine no problem with timing. Just leads out 180.

Greg H

I was actually thinking the top vac advacnce plate in the dist could be 180 but don't think the leads were crossed before when it was running. The only thing that could be different is the dist drive from when I rebuilt the engine. I put it in on the bench so it's as per the manual but is my manual wrong? No problem for me to rotate it if it is.

Greg H

Hi James,
just offering more background info trying not to assume by asking for more info as comfirmation

with people who know exactly what they're doing like yourselves you can sometimes overlook school boy errors that the less informed can make - I've not put that well

now I not for a moment suggesting Greg has done this just an example of what can happen that you wouldn't occur to ask about - to cut a long story short a chap managed to fit a dissy cap on the wrong way round - it wont fit - chap "tes it was very difficult to do up"

again I stress - I'm not saying Greg has done anything like this

years ago when CDs first became popular a freind of a friend, over the phone, can't get his new CD player to play the CDs, I went through everything nothing worked told him he'd have to take it back to the shop - turned out he was loading the CDs in the player upside down which I couldn't see over the phone and was so obvious which way the CDs loaded I never thought of it - I assumed it was obvious and was known without giving it thought

ETA: Greg, I don't known please don't ask me - looks like you could be 180 out :)
Nigel Atkins

Nigel as you can see I haven't sorted the oil pipes yet. The pipe places are closed on weekends so I haven't been able to get the new ones shortened. I've been looking for an orginal metal pipe and not run the cooler but haven't been able to get hold of one of them either, they're quite elusive. It's a slow process...
Greg H

Do you know Greg I didnít even notice that oil pipe but I did the industrial lead from battery to starter solenoid

and its so much easier to see things on a clean engine with bonnet and panels missing (well for most folk)

parts are always a weird thing as you know somewhere people have them lying around unused and unwanted but you donít know who and where, always amuses me that you can have for sale and wanted columns next to each other with the same bits in

if youíve got a part number Iíll search this end
Nigel Atkins

If you've changed the distributor drive you may have put an early one in as they were 180 degrees out relative to later ones. I had to put mine in upside down so the distributor pointed the right way.
F Pollock

The original battery lead had a bit too much volt drop and that one was at hand so it's a temp fix. I still need to fit the oil gauge. Not a lot of use next to the battery.

The metal oil pipes are no longer made but you can buy stainless braided pipes with fittings for about 20GBP but I'd rather an original metal one if I can. They come up now and again and I'm not waiting on it just yet. It's a TAM2106.

One that's a bit harder to find (worth a gold star):
My grey cockpit moulding AHA8058. I bought a black one but didn't like it. It didn't fit as well.

Another thing I'm after is the heater blanking plate 14A4709 (Moss p79). Covers the heater hole on those cars that don't have a heater. Now if you can find one of these I'd even buy you a pint of the warm stuff. I'll probably just make a plate for it but if the orignal has a bit of shape to it it'd look better.

So back on topic. It's the same drive but don't recall how it was before I pulled it apart. Is the manual out 180?
Greg H

Haynes is 180 degr. out. BTDT.

Maybe you put the top shaft on bottom shaft 180 degr out? Drive dog on dizzy can't be off, roll pin is off center IIRC
Alex G Matla

The pin is central, so it is posible to fit the drive dog 180 out on the shaft, although most people don't dismantle the dissy to that extent.
Dave O'Neill2

Ok so have it sorted now. I checked it again and the drive was where I think it should be but the rotor was pointing down bottom left towards the starter.I thought I might be able to spin the drive around on the end of the distributor. I know Alex you said it was offest but it looked symetrical. So I spin it around and tried to tap the pin back in but it only went half was because you were right it is offest. So I span the drive shaft around. I found a great tool to do it with too. BMC special tool no. DIST001 more commonly known as a hard top securing bolt. Pic of the drive before and after I rotated it. No.1 on TDC. The rotor buton now points top right where it should. Why the problem I don't know but it's sorted.

I'm onto my next little challenge now getting the windscreen back on the car with a new body seal fitted to it. :(

Greg H

I must admit, I would struggle to spot which segment was the larger on that dizzy drive! I believe taht some of the early cars didn't have an offset anyway, but that on early MK 1 sprite engines I think. Not relevant to yours.

Next one - "getting the windscreen back on the car with a new body seal fitted to it."

This photo might help with that one!


Yes not easy to see form the pics but the little half is at the top now. Guy thanks for the good idea for the screen. I've got it sitting on there with just a pin in each side. It will need a bit more force to pull it down. That would work ok if I had doors on my car. I might try it with just the hinges bolted on and if it doesn't need too much force it might still work. If not I may have to put the doors on.
Greg H

Yes I can (just about) see that the two halves on the drive pinion shaft are different, but it isn't very obvious is it!

I used the ratchet strap idea last year. They are just cheap straps but they get enough of a pull down on the screen to make it a one-man job getting the rubber seal compressed enough to get the fastening bolts into place. The angle with it pulling on the top hinge is just about right. I guess you could just put the hinge on but won't you need to have the doors in position anyway to get the screen angle matched to the quarter light?

I can just make out there are 3 photos about the dissy

that tool is also an official TVR exhaust fitting

Iím drawing a blank with that TAM2106, you could try contacting MG breakers to see if they have a bust engine I suppose, the Wrexham lot look like they value every bit on a car

the heating blanking plate I donít think weíd have much of over here, it reminds me of a rare part I wanted for a different car I found one in USA but just my luck someone else wanted it and I ended up having to win it at about £50 Ė two weeks later the same part came up in the UK and didnít sell for £1 !! itís often just a case of luck/timing or what ever else you want to call it but the further and longer you look the better the chance

still working on grey cockpit moulding

obviously I must point out your mistake the beer here isnít warm itís just that it doesnít need to be chilled to hide the lack of taste or have gas added to make it look less dead :)
Nigel Atkins

The cross pin holding the drive dog to the main shaft of the distributor is drilled slightly off center. When assembled correctly, the cross pin fits smoothly and snugly. When assembled 180 different, the holes do not properly line up and the pin has to be forced into the holes, deforming slightly as it does so. Often, the pin cannot be fully seated and you notice a piened over end on one side and that the pin is not fully through the drive dog on the other. Never a good idea to "rotate the drive dog 180 degrees".

The distributor drive gear can be removed, rotated 180 degrees and re-installed.

The easiest method, however, is to remove the points cam, which is attached to the mechanical advance mechanism, rotate it 180 degrees, then reassemble. It is quite easy to assemble the points cam either correctly or 180 out and many not familiar with the distributor rebuild process will do so. Easy to check and easy to correct.

Les Bengtson

Nigel very pleased to hear you're looking for me. I managed to picked up an good original 6 spoke steering wheel so that's one less bit I'm hunting for. You're right the beer wouldn't be warm at the moment, even the bitters would be extremely cool. Good thing that midgets got a heater in it. lol

Les where were you at post no.2??? I was asking whether the top of the dizzy could be spun around. :( I suspect that's the problem as I did rebuild the distributor when I first rebuild the engine many years ago. So do I now swap the top of the dizzy and also put the shaft back to the correct spot to keep myself happy? I'd like to, but I'll just have to let it bug me for now because I've got a few more pressing jobs to do first. I'll do it later on. :)
Greg H

That's what I ment with this: "Maybe you put the top shaft on bottom shaft 180 degr out?"
Alex G Matla

I love the sprung spoked steering wheels, I bought a repro one for my previous Spridget, at that time I had to hunt around for the copper slip ring (and obviously you'll also need the boss and horn push)

you'll be glad to know over here good pubs look after their beers and the cellars are temperature controlled so the beers aren't too cold or too warm regardless of the time of year - fizzy lagers are always too cold but that's how the advertisers tell the kids they've got to drink them, luckily we have many different beer styles to chose from including bitters and proper lagers :)

it might be cold but there are still many things to be happly with over here :)

still chasing your grey plastic, all is not lost (yet)
Nigel Atkins

Well my curiosity and fussyness got the better of me. I pulled the dizzy apart and span the top half of it around and then put the drive shaft in the engine back where it should be. Happy now.

Alex I thought that was a question you were answering i.e. Could the bottom of shaft i.e. drive dog be 180 out. No it couldn't as the pin was offset. I didn't realise you were talking about the two halves in the dizzy. A bit slow on the uptake but I understand now.
Greg H

sorry your post has reminded me I got nowhere with chasing the grey plastic with suppliers

I think someone suggested painting the black grey

or just put black in and have the hood frame black

purist will tell you exactly what was on a car when it was produced which is amazing really considering they weren't there to witness it

I had a car that was previously owned from brand new by my neighbour that was a very original car when a marque expert bought it from me he couldn't accept that the dash was original from factory because it wasn't the same colour as it 'should have been'

I'm sure from MG. BMC, BLMC, BL there were a few unnoticed production cars with anomalies, basically on production they used what was available at that particular time and I don't think all changes of components were a guillotine change over Ė hence the confusion of change over points for components
Nigel Atkins

This thread was discussed between 12/02/2012 and 21/02/2012

MG Midget and Sprite Technical index

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