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MG MGA - Tight Red Rotor Arm

engine just stopped all of a sudden the other day. The time I got around to checking for a spark (10 mins) it fired up on 3 cylinders. I reconnected HT lead to spark plug & all was OK.

I ordered & just fitted the recommended red rotor for 25d dizzy. One of the stated improvements to these is that they have a strong steel clip & tight internal tolerance to ensure a tight shaft fit. They're not kidding, it’s on (with force) & engine ran well after a long test run in sunny UK today. Not sure I will be able to remove it without any damage, good job I ordered two. Anybody else observed this? Perhaps it may loosen in time.

Richard
R A Evans

Mine was very tight. I seem to remember having to file the locating lug to get it to fit.

Steve
Steve Gyles

Interesting. I've been using the red rotors on 25D distributors in both my MGA and Morris Minor for several years. They are a snug fit but never had trouble pushing them on or pulling them off.
Andy Bounsall

Andy

I should have said that my distributor is a Chinese replica so I was not overly surprised that the rotor was a bit tight.

As an aside, 3 years down the road, the distributor is working fantastically. Best advance profile I have had on any of my previous Lucas and Aldon distributors. Cost me £60 from Bob West. I stripped out the points and put in the Flamethrower (pertronix) electronic ignition. The only problem in the 3 years of running was the rotor, causing restarting problems. Sorted once the red rotor was installed. I dissected the old rotor to find evidence of the arcing. Photos are somewhere in the archives.

Steve
Steve Gyles

I fitted a red arm a few months ago, and agree with Andy - snug, but not difficult to fit and remove.

Robert
Robert Sinclair

My red rotor is a perfect fit. It is fitted on an original 25d Lucas distributor. Never gave any problems yet.

Frank
F Camilleri

I'm interested in all this as I was on the verge of buying a red rotor arm from 'Distributor Doctor' over here.

Is it beginning to look like the cause of the tight rotor arm is a non original distributor rather than the rotor arm itself?

Do you still have your original (Lucas)distributor to try your red rotor on Steve?

..........................Mike
m.j. moore

Funny you should ask that Mike. It occurred to me a few minutes ago to try my spare red rotor on my old Lucas Distributor. I will go and brave the cold and check shortly, after I have done the washing up!

Steve
Steve Gyles

Just tried my spare red rotor on my spare Lucas DM2 and 45D distributors. Very tight fit on both compared to original black rotors. Left shavings of red behind on the shafts. Got them from Bob West. Are the red rotors all from the same manufacturer?

Steve
Steve Gyles

Just got this from Martin Jay's site about red rotor arms:-

" Like most good ideas, we’ve suffered from low grade pirated copies being sold very cheaply, so BEWARE CHEAP COPIES OF MY RED ROTOR ARMS.
I'VE EVEN SEEN THEM POPPING UP IN GREEN LUCAS BOXES RECENTLY.
As of late Spring 2012 all my genuine red rotors will bear the DD marking."

............Mike

m.j. moore

That's probably it Mike. Mine have no markings. Mind you they are from a respectable supplier and could be from a pre-Spring 2012 batch.

The plastic material seems quite soft compared to the black version. You can see in the attached photo how the internal wall has been marked and scraped, and the lug has been shaved.

I was charged £2.50 each + vat and postage.

Steve


Steve Gyles

I got mine from Powerspark Ignition Ltd (through Flee bay).

Mike, I recommend that you continue with your purchase from ‘Distributor Doctor’

Richard
R A Evans

I've also heard the Distributor Doctor supplies the right ones. With regards this tightness, its worth checking there is no sign of any rust around the rotor's shaft, had this with a pal's MGC. Nothing a bit of 'scotchbrite' couldn't cure.
Pete
P N Tipping

Pete, no rust on any of the shafts on my 3 distributors. You could feel a very obvious difference pushing on a 'newish' black rotor compared to my red rotor. I tried on all 3 distributors and experienced exactly the same results. By the end of my tests the red rotor had been on and off probably as many times as the old black one, so it was a reasonable comparison.

Correction to my pricing, I misread the breakdown of costs on my invoice. £5 was the unit price + vat, not for the 2.

My rotor may or may be not an original, I will endeavour to find out from Bob. In the meantime, a general question to anyone who has a 'genuine' red rotor, is the material noticeably softer than that used for the old black (bakerlite?) rotors? i.e. can shavings come off as happened with mine?

Genuine or copy, mine is working fine on the car, so I am not planning on buying replacements just yet from the DD.

Steve
Steve Gyles

I paid £7.45 inclusive of VAT for my pair of red rotors. My old black rotors are hard & feel almost glass like (bakerlite?) compared to my softer (probably non genuine) red rotors.

Carried out an internal measurement on both units:
Black is 0.566in
Red is 0.556in
Therefore 10 thou smaller in diameter.

Unable to carry out an accurate measurement on the alignment peg but both rotors look very similar in width. Steve, from your picture it looks like your peg is too wide.

Richard
R A Evans

Distributor Doctor sells for £6.00 plus vat each and the total, including p&p for one is £11.40. It also looks as if Accuspark sell DD rotors at about the same price so about double the above.........Mike
m.j. moore

This thread was discussed between 19/02/2013 and 21/02/2013

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