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MG Midget and Sprite Technical - Distributor rotor

Should you be able to rotate the rotor arm whilst the engine is stationary?

I have a feeling that you shouldn't, however mine does (and the car doesn't run, although there are many possible reasons for this). How can I reset the timing and reconnect the distributor shaft?

BH Harvey

either the dizzy clamp has come loose and has popped out of the engine a bit or shaft has broke or worse. can you turn the dizzy,if you can its just popped out.
regards bob.

I am in Greenhithe. Are you anywhere near me?
Alan Anstead

Rotate it how far, and do you mean just the rotor or the distributor shaft also? It is normal for it (with the shaft) to rotate as far as the advance mechanisms will allow.

C R Huff

As charlie says, the rotor arm will rotate a few degrees agains the springs, and then should go back to it's position, --- allowing for some play.

If yours rotates freely all the way around, you have a problem. Either the shaft is loose or the rotor arm is loose on the shaft.
Lawrence Slater


Just pushed it back into place, it still seems a little sloppy though. The clamp is also fully tightened, yet I can remove the distributor without touching it, should it clamp it in place?

How can I check if the timing is 180 out, or is it just trial and error?
BH Harvey

Been a while since I worked on the Spridget, but I think it is like the B, which makes me wonder if your clamp is bolted to the block. It should be.

C R Huff

If you are not too far from me maybe I could come and sort it?
Alan Anstead

If the clamp is fully tight, you should not be able to move the distributor, that's it's job to clamp it. To check the distributor is not 180 deg out. Make sure no1 piston is at TDC, you can do this by removing the spark plug, looking down the hole into the cylinder, you should be able to see the top of the piston. It's not important to have the piston bang on TDC. The rotor arm should be pointing to no1 cylinder. It could be that the 2 bolts that hold the clamp onto the engine block are to tight to enable you to tighten the adjustment. it might help if you loosen off one of the bolts, tighten the adjustment bolt and then re-tighten the retaining bolt.
Pete Ottewell

Easy to tell whether you're 180 out.

Just take off your valve cover and remove the spark plug from no. 1 cylinder to look inside with a flashlight. Rotate the crank pulley clockwise (I just use my hands on the fan belt--make sure the ignition is OFF when you do this!!!), until both rocker arms are slack on no. 1 cylinder and you can see the piston rise to TDC, and then carefully align the timing mark on the puller to TDC. (Check your manual for a diagram or photo.)

At that point, the rotor should be pointing to the no. 1 cylinder's spark plug lead coming out of the distributor cap. If it is, you just insert the remaining wires into the cap the proper firing order, going in the direction of distributor rotation--and you're done!

JM Young

The clamp is attached to the engine block with two bolts. With everything tight it shouldn't move. Sometimes getting the clamp tight can be an issue- I've had the bolt which goes through the clamp bind up before the clamp grips the dizzy. Alternatively I wonder whether you have the wrong clamp? (Are there different size dizzy bodies?)
Graeme W

Can the dizzy be put back 180 deg out? The drive dog is offset so it only goes back in one location. Thinking back 40 years now, so it's a bit painful!
Graeme W

If the clamp is tight but the dizzy can still be turned, its not unknown for the cast metal ring at the foot of the dizzy to have shattered, crushed by the clamp. If that's what has happened, you may have to source a replacement. Pull it out and have a look.
Mike Howlett

if the clamp has been repeatedly overtightened it will have twisted and distorted so that although apparently tightened up the clamp no longer grips the dizzy body. The solution is to take the clamp off and straighten and re-shape it back to original.
Guy W

@Alan Anstead. Thanks for the offer, however I believe that I have it sorted now.

I have reset the distributor in relation to the TDC of cylinder #1. I also prised the clamp open to allow it to accept the distributor body (I should have mentioned that it is a 1500, thus the clamp only attaches with one bolt).

Could anyone confirm whether this is the correct order for the spark plug leads? I'm certain that #1 is right but not the others.

BH Harvey

The firing order should be 1-3-4-2
Pete Ottewell

it looks like you got 2431 on your timing....but I cant see the spark plug wires very well

Prop and the Blackhole Midget

dissy 1 to spark plug 1
d. 2 to s. 3
d. 3 to s. 4
d. 4 to s. 2

Prop and the Blackhole Midget

dissy is counter clock wise
Prop and the Blackhole Midget

I don't have a midget manual to hand and can't remember the firing order and dissy rotation for the Triumph engine.

Don't assume that it is the same as the A-series.
Dave O'Neill2

OK, a bit of googling suggests that the firing order IS 1-3-4-2, as per above.

If the dissy rotation IS anti-clockwise, your leads are in the wrong order. Your leads are 1-3-4-2 clockwise. You need to swap 2 & 3
Dave O'Neill2

It is definitely anti-clockwise and firing order 1-3-4-2. I had a mate with a Spitfire, wash my mouth out, back in the day who had the leads in the wrong order. I took the p'~s relentlessly for a long time after I put him right as he was always telling us how good he was at tuning engines.
Pete Ottewell

Maybe I'm suppressing memories of the Triumph engines I've owned ;o)
Dave O'Neill2

earlier this year I put up a thread titled ‘Firing order’ to help exactly with this question, before all the p*ss –taking from others there’s an excellent photo from FRM of the lead positions and I added text

to save looking here it is (minus the humorous comments) –

>>thanks to FRM for the very clear photo of the Triumph engine dissy position and HT leads layout appropriate to the Midget 1500

again the firing order is 1 – 3 – 4 – 2

number one cylinder (far left of photo) is nearest to
. the radiator
. the front of the engine
. the front of the car

as you look at the distributor the rotor and thus firing order from the rotor goes anti-clockwise (counter clockwise, CCW)<<

Nigel Atkins

Take the p@#s out of the keeper of the book, who would be so bold?
Pete Ottewell


I assumed that the rotor would go clockwise (that seems right), however after these replies I spun it over and it most defiantly goes the other way.

I shall go on the authority of that Spitfire picture, thanks for digging that out of the archives Nigel.

BH Harvey

This thread was discussed between 29/12/2012 and 31/12/2012

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