Model A - magneto

 As usual, I will be using the services of Mr Tony Cooper of Halesowen to rebuild the magneto for the Model A. I spoke to Mrs Cooper today and learnt that Tony would be able to rebuild the BTH KC1 for me. He's done the magnetos for both the FH and the W/NG, and they are excellent - the estimate for the Model A was a maximum of £250 and it would take 14 to 21 days.

This is how the magneto looked when it arrived. It's more or less the right period for the Model A but as you can see it is a slack wire advance magneto - Ariel specified a tight wire advance magneto. In theory, slack wire advance is a better option because if you lose the cable, the engine will still run optimally at speed - but it might be rather hard to start!

First job then is to remove the magneto. Fortunately this side of the engine is relatively clean and it's quite straightforward - it's just the same arrangement as the W/NG, built 12 years later.

Underneath I was surprised to find only two bolts holding the magneto down - the magneto is set up for four bolts, the W/NG uses three. 

With the magneto chain cover removed we can have a look inside for the first time, and it's all pretty familiar and pretty clean although the chain is very loose indeed:

All you have to do is remove the magneto retaining nut and then use the usual magneto pinion puller to release the taper:

You can then remove the two bolts holding the magneto to the platform and lift it out of the way. There appears to be a seal between the magneto and the chain case which looks like it is a felt seal sandwiched between two pieces of tin - it's black and oily at the moment so when it's cleaned up we can have a proper look.

Here are a couple of before pictures of the Magneto after it's had 15 minutes of fame in the parts washer:

Looks pretty good and turns easily. There's something wrong at the points end though - the bolt retaining the points to the armature makes contact with the brass end cover. One of these parts must be wrong, probably the end cover because in this arrangement the magneto will always be earthed and will not spark. 

Tony Cooper will sort all this out!