Dominator bottom magneto nut

Horrible job. I sacrificed a spanner and ground its sides and faces until it fitted. Luckily the P.O. had fitted stainless bolts so once it was slack it could spin off and not need 1/8 turns forever.

There's a 'tech article' in this site all about it containing the advice I was given by NOC experts some years ago.

Good luck!

Once you get the wretched nut off, replace it with the long bottom nut from a BSA twin and never have this problem again.

Previously keith_parsons wrote:

Hi

I need to change the mag on my 58 dominator engine, but even though I've taken off the timing cover, oil pipes and footrest I can't get anything on it.

I've got a selection of 1/4 whitworth spanners.

It seems only a very thin open ended has any chance.

DoI cut one to length and file the jaws?

Or do I have to take the engine out?

Any help would be appreciated.

Thanks Keith

no you make your own 1/4 spanner cut out at the side so you can get to the nut. this is very easy to do with a length of flat bar, and cut out at on end only the size of you nut and file up the rest. this basic tool making we did at school at aged 11 in metal work

Previously anna jeannette Dixon wrote:

Previously keith_parsons wrote:

Hi

I need to change the mag on my 58 dominator engine, but even though I've taken off the timing cover, oil pipes and footrest I can't get anything on it.

I've got a selection of 1/4 whitworth spanners.

It seems only a very thin open ended has any chance.

DoI cut one to length and file the jaws?

Or do I have to take the engine out?

Any help would be appreciated.

Thanks Keith

no you make your own 1/4 spanner cut out at the side so you can get to the nut. this is very easy to do with a length of flat bar, and cut out at on end only the size of you nut and file up the rest. this basic tool making we did at school at aged 11 in metal work

Must have hit the wrong key! Just re-posted Anna's comment. What I meant to say is:- After getting the mag off for the first time (Grind the sides off a spanner, as previously advised), why ever go through the fiddly procedure again. Even with a modified, or hand made spanner, you can only turn that bottom nut one flat at a time. Go for Gordon's answer, the BSA item will make it easier to replace the mag, and, sod's law being what it is, having made life easy, you will probably never have to take it off again!!

On my '57 Dommi (M77) I wanted to leave the original arrangement, so I modified a used 1/4W wrench , which included shortening its length. The whole process only took about 10-15 minutes with a bench grinder.

But for practical purposes the BSA type long nut is the bee's knees. You can buy them in plated steel, or stainless steel for less than you could buy the stock & make your own (unless you have free material & time). It would make for an easier time if you were on the road & had to remove the mag.

Either way works, pick your poison

The Extended BSA nut is by far the best solution to this problem.

But..........I have noticed that these do vary in thickness and the fatter versions may foul the crankcase halves or magneto body. This may, then in turn cause them to start the thread end out of line and possibly mess it up.

So, do check for clearance before refitting the magneto. If the bolt needs to go on a diet just stick it in a drill and grind enough metal off to make an easy fit.

The cut down spanner is agood idea to aid removing an original magneto nut. A very useful tool in my collection is a Bedford 1/4" x 5/16"ring spanner. See attachment. Thisis incredibly thin and very tough. It allows me to get at that lower magneto nut and turn it enough to loosen. This spanner also fits inside the cylinder barrel fins totackle the underside head sleeve nuts and also the real wheel brake drum/sprocket sleeve nuts.

If you can find one, (I have not got one any more) the next size down 3/16" x 1/4" allows nearly a quarter of a turn on that magneto nut.