MagDyno Fitting

[James Hickman]

I have a 1951 Ariel NH 350 that I am restoring. It has been in a barn for 30 years and came with a tatty MagDyno, that is missing its end cap and will need refurbishment.

I gather from Draganfly that it should be an MOIL (The MO with the longer 60W dynamo) and does look like it to me. It’s drive sprocket was fitted to the chain so it appeared to fit. However it was sitting loosely on its mounting plate. I assumed the bolts that fix it to the mounting plate were just loose - but when I removed it, I found it just had 4 small “feet” rather than the expected tapped holes in the bottom.

The mounting plate has three holes that it appears that it should be bolted to.

I wonder if it is a replacement from another machine (I gather some BSAs were just strapped down?) Should I adapt it by grinding off the little feet and drilling and tapping the base plate? (or have I misunderstood how it should be fixed down? )

[dave.owen]

The 4 feet are plugs and can be pulled out. You can drill and tap the three holes required to fit it to the Ariel engine plates.
Dave

[James Hickman]

So they are!

[pete.collings]

That was the magdyno fitting for BSA singles, as Dave says the two drive end holes can be tapped 3/8" BSW (drill hole to 5/16"). When drilling the centre hole for tapping, I use an engine plate as a template to ensure the hole wil be in the correct position. You can drill the hole without dismantling the magneto, but be very careful to check the depth of the existing holes and use a stop on the (pillar) drill to prevent the hole going right through to the inside of the magneto.
If the holes for the pegs are shallow, you may need to deepen them, checking one of my mags gives a depth of just over 5/8"

[nevhunter]

You only need to thread the 3 required. Get full depth in the mag base with a plug tap or make one from a broken example. Try not to go too deep and penetrate the internals.
Sometimes the underside of the plate it sits on, has wear around the oval holes that make adjustment difficult. It's important to have the magneto sitting square to the case for chain life, so weld and reface the area around the slotted holes. It's a worthwhile thing to get right. Don't forget the small bolt fixing the two rear engine plates together below the battery box, and the spacer on the footrest long stud between the engine plates, or they distort when tightened. Nev