MG5 Dynastart electric starter.

[andyfrost]

You say you have done a “strip and rebuild” of the magneto , but have you actually had the coil and condenser properly tested , spinning it with a drill will not directly identify your problem.

Andy.

[ransomes256]

Iain,
Now you have it timed to TDC mark the position of the magneto then retard it a little (turn it anticlockwise) This should aid starting but will drop max revs and power a bit.
If you have been trying to start it a lot you may have lost some compression due to bore wash. Try squirting a bit of oil into the bore.
Are you keeping the carburettor flooded to ensure engine can suck fuel?
Starting procedure I have found most effective is.
Spark plug lead off.
Full choke.
1/4 throttle.
Flood the carb.
Pull engine over 3 times slowly.
Put plug lead back on.
Flood the carb. again.
Pull over to start.
Good Luck.
Neil

[silverfoxfintry]

The condenser is new. As for testing the coil, can anyone tell me how to test it.
Will an electric motor insulation tester be sufficient? I think they produce about 5,000volts.
Or is a special test rig required?

Thanks.

Iain.

[expeatfarmer]

Iain
I had exactly the same scenario with the magneto on my MG2 137 eventually I fitted a replacement magneto and it has never been an issue since but I worked for days trying to get it to run on the original which gave every semblance of being serviceable. Have you a machine nearby you could borrow a mag off?

[silverfoxfintry]

No. The only one I know of is not available for a borrow.
I have asked. But no chance.

[trusty220]

One test that you can do when running it on the drill is to decrease the speed gradually (you need a variable speed drill for this) and watch what the spark does. I’m guessing that once you get down to a speed equivalent to tick over or just above the spark disappears. This would indicate a coil that is starting to break down internally and the only remedy is a replacement coil.

Best of luck.

[andyfrost]

Take the coil to your local(reputeable) garden machinery dealer , he should have a purpose built ignition tester , have it tested and go from there.
Coils simply cannot be tested properly with a multimeter.
My money is , and always has been a duff coil.

Andy.

[roatavator]

Iain, here’s a link to Sean’s excellent restoration of a 56 which you might find useful if you haven’t already seen it.
There’s a lot of information on magnetos and where he got parts from. Or, just a thought, there’s a few cheap series A’s on that auction website at the moment with good sparks which you could get the coil from.
Peter

Simar 56A Rototiller – Serial No. 561621

[expeatfarmer]

Iain
I had a very similar experience with my MG2 137 the magneto had a label on it stating that it had been rebuilt, fat spark when driven by a drill but fitted to the engine bang bang was all I could get I persisted for days trying everything I could think of and then eventually I fitted a later mag and the engine started first pull and has continued to run perfectly ever since. Do you have a friend or member nearby that has an MG5/6/40 that would lend you a running magneto to test on your engine?

[expeatfarmer]

Where is it that you live? Sorry for some reason my page has only just updated I thought my previous response had not been listed. JC

[silverfoxfintry]

I live to the north of Glasgow. Tucked in behind the Campsie hills, in a small village called Fintry.
Only 20 miles from the centre of Glasgow, but it’s another World!

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[wristpin]

I’ve no specific MG knowledge but the general principle for setting timing where there is an impulse starter is to turn the engine until the impulse trips and the turn it back to set the timing. Setting to TDC seems a bit wrong, is there not a BTDC figure?
On the subject of bench turning mags with a drill or even just flicking them over, the HT lead should always be connected to a properly gapped and earthed (to the mag base) plug. Not giving the spark somewhere to go can lead to internal tracking and a ruined mag.

[roatavator]

Iain, reading back over the posts, your “bang, bang,” might imply timing. Did you really mean you’d set it to spark at TDC? If so you need to set it to BTDC. Don’t know the exact setting for your application but I’ve attached a front photo of a SIMAR. The two round marks on the flywheel case are about the right distance apart.
Other than that I might suspect the impulse mechanism not working properly, as you are certainly getting a spark at low revs.
Peter

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[vhgmcbuddy]

Have you tried a different spark plug?

Mate of mine brought an MG6, we got it going & fitted a NGK plug. It ran fine till it packed up. He messed around for days with it till I went over. All it would do was bang & back fire.

In the end we fitted an old Champion D16 plug from an stationary engine & bingo she runs a treat!

[wristpin]

Mate of mine brought an MG6, we got it going & fitted a NGK plug. It ran fine till it packed up. He messed around for days with it till I went over. All it would do was bang & back fire.

In the end we fitted an old Champion D16 plug from an stationary engine & bingo she runs a treat!

That’s an interesting observation – my Dennis does not like NGK plugs. It will run on a new one but once stopped will not restart on it . It’s perfectly happy on old Lodge or KLG plugs.
I cant remember the exact detail but there has been previous correspondence on this forum about modern plug insulators being un-glazed? and getting contaminated by the products of the combustion of ethanol fuel – I think!

[Author]

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