[wristpin]

Unfortunately there is a whole generation of so called garden machinery specialists where the knowledge base is limited to rotary mowers with electronic ignition. It may be possible to recover the damage to your coil if there is enough of the terminal left to solder a tag wire to; an old school radio or electronics repairer or even an amateur electronics enthusiast may be your best bet as there may be just one chance to get it right.

[wristpin]

That is the same set up as on my Shay. Fortunately my coil was ok and the condenser dud. I used a Briggs condenser which worked OK but a Meco module would replace both the points and the condenser.
Have you actually had the coil tested on a proper ignition tester – or just jumped to the conclusion that it has failed?

[wristpin]

Guess work until you post an image or two!

[wristpin]

Ok, so the ignition is from a flywheel magneto which does not require an external power source. Your black wire is most likely the “ kill wire” to stop the engine when earthed via a switch. As your machine had electric start the “ ignition” switch would probably performed the kill function when in the Off position. With that set up you must be careful to get the wiring correct . Getting it wrong and feeding battery voltage through the ignition coil will most likely destroy it.

[wristpin]

As usual, a couple of images will bring your post to life – picture worth a thousand words etc!
So, the dynastart looks after battery charging and starting but is the ignition from a self contained flywheel magneto or an externally mounted automotive type coil fed from the battery and fired by either internal or external points?

[wristpin]

Never had an issue of any sort from using a piece of quality synthetic starter cord – the larger diameter the better.

[wristpin]

Various versions of that are available but really only suitable for 2 stroke applications where the spark plug is immediately above the piston. A length of heavy starter cord stuffed into the cylinder through the plug orifice is just as effective and is
“universal” !

[wristpin]

That makes more sense, so I suppose that the next step is to check that the impulse is actually tripping at TDC at cranking speed.

[wristpin]

The MG5 manual is quite specific, the impulse timing is set at TDC

So, where does that leave the timing once the impulse has tripped?

[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!

[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.

[wristpin]

Your numbers indicate that you have a points ignition 5HP engine that would have been fitted with a 397398 coil which has been replaced by a 397358 Magnetron electronic coil that does away with the need for the points and condenser and may be fitted without removing the flywheel.Roughly £40 + vat)for a genuine BS one.
As per per my earlier post, you may well be able to pick up a good used one from a engine scrapped for some other reason. What you need is Magnetron coil from a 5HP 13**** series engine (either vertical or horizontal crank). Before you go shopping, carefully measure and note the distance between the coil supporting pillars on your block and check it against any coil that you are offered as there are fractional differences between engine sizes.
A quick measure on a 5Hp block in my workshop (dark and snowing!!) is approx 59mm BUT PLEASE CHECK FOR YOURSELF.

[wristpin]

I’m guessing that you have a Briggs and Stratton engine ? If so, stamped into the blower housing ( the shroud that carries the recoil starter) you should find the words Model, Type and Code. Below each word you should find a series of numbers. Assuming thayour engine still has the original housing, those numbers will identify it right down to the day it was made and even the production shift.
This will determine the coil that you need. Pre ‘79 it is likely to be a points ignition magneto – that is, under the flywheel will be contact breaker points and a condenser. The good news is that a modern Magnetron, electronic ignition coil may be fitted, without having to dig around under the flywheel. Even better, most small engine / mower repair shops will have a box of good coils removed from scrap engines .

Example only, your numbers will probably be on the vertical face behind the carburettor.

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[wristpin]

My personal opinions – not recommendations .
Villiers Parts , good quality stuff, may be a bit erratic on communication. Definitely still there just before Christmas.
Villiers Services . Good and well organised but mainly for motor cycles . Useful where bike and industrial / Hort overlap.
Meetens . Expensive, maybe? but unsurpassed for depth of stock and freely given knowledge. Will often help out with good serviceable used parts.
L&S. Variable quality and descriptions. Maybe I’ve been unlucky.

[wristpin]

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