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MG MGA - Starter Question

Background. In Spring last year my original BMC starter failed. My engine is 3 bearing 1800. I got a new replacement from Moss but this summer, after one summer's use, it went weak, i.e. it would often take several goes before turning the engine past the first compression. I spoke to Moss who were happy to swap it, so I now have another of the new Moss motors and although much better it still occasionally struggles. By the way I have never failed to start in the end, and for reassurance I have the handle.

My question is whether it is reasonable to expect this starter to work on a std 1800 engine? Presumably the original B starter was similar if not identical? Or do I really have to take the Steve route and go for the much more expensive modern pre engaged one?

Paul Dean

One assumes the battery is in good nick! Before you go down the road of another new motor. Check and clean the battery connections, including both ends of the earth cable, also the starter connection although, I suppose you did that when you installed the motor. Check that the engine earth has good connections at both ends and isn't showing signs of corrosion.
Allan Reeling

And the ignition timing, if it's advanced too much it'll fight back on the starter, specially first start for the day
William Revit

I had the original starter from my MGA 1500 Coupe rebuilt as part of my restoration and am using it with my 1800 3-main 18 G engine. No problems.

If you still have your original, have it rebuilt.

JL Cheatham

Sounds like a bad ground to me. Remove the battery ground and clean the connector and mating surfaces spotless. Apply a bit of di-electric grease and put them back together. Next do the same for the ground strap between engine and chassis. Then clean the starter connections as well, and all should be good again.
Steve Simmons

I think I might have found the issue. It appears it isnít one bad connection but multiple slightly bad connections that only get slightly hot. Good to be reassured that I donít need to go for the expensive option.


Paul Dean

Which connections were the main problem Paul? Or was it all of them?

I have had similar starting issues with my car pretty much since I first got it around 12 years ago.

It had a 1840cc 3-bearing MGB engine like yours at first but now it has a 1950cc 5-bearing motor.

I have recently changed to a twin 12v battery setup and also replaced the main battery cable to the starter switch with a much thicker one than the original but it hasnt really improved things much. It has always started up but it still sometimes turns over a little reluctantly.

The starter motor is a fairly new standard inertia starter.

I did have a high-torque starter motor in the pipeline but before I go that route I plan to replace all the earth cables and I wondered from your comments if there was one prime suspect that I should look at first?

Colyn Firth

Good to hear all ok Paul. You can sort all the connections except one - that dreaded starter pull switch internals. Bypassing the heavy load on that switch with my 'expensive' hi-torque pre-engaged starter was the best thing I ever did.

Steve Gyles


Only had a quick check but so far it is pos battery terminal, now fixed, the other end of same cable where it bolts earth to the battery carrier and the output side of the pull switch. My pull switch is original and I think it is heat just coming from loose terminal nut rather than the switch internals. I will get them all sorted in next week.

Paul Dean

I rebuilt my own starter and while it was kind of a pain, it was eminently do-able. The biggest challenges in doing your own are getting the commutator turned, and soldering in the new brushes. I was lucky enough to have a machinist friend able to chuck the armature up in his lathe and clean up the commutator... One nice thing compared to overhauling a generator, is the insulators for a starter commutator don't need to be undercut after turning.

Some of the brushes are connected by large gauge wires that must be soldered in place. A normal soldering iron won't do the job (not even my butane powered one would); it took a fairly high output iron to get the wires hot enough. I was able to borrow a suitable iron from my brother.

The rest is just regular disassembly/clean/reassembly/paint. You have to replace a couple of bushings, but I don't recall there having been too much difficulty there.

Barney has some of my starter pictures on his site here:

D Rawlins

I have used stock early starters with high compression race motors - essential to get good ground connection.

If you want a 'trick' you can obtain a starter from a Morris Marina. They are pre-engaged type and the tooth bevel is the opposite way, but it doesn't matter. They have more torque. Don't get the MGB all synch starter as the solenoid is 'clocked' in the wrong place and will hit the frame.

I use one on my 12:1 Twin Cam. Spins it plenty fast.

Here is a picture. Don't get confused by the engine - it is a 5 main 1800 converted to Twin Cam head. The rear engine plate and flywheel is a stock 18GB style, but the starter will also fit a high mount MGA (15GD and later). Not sure if it also fits the older low mount as I haven't tried it.

You can of course just buy a high torque Japanese starter from various vendors if that pleases you.

Bill Spohn

This thread was discussed between 03/08/2018 and 11/08/2018

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