Lucas PA Speedometer repair

First, read Douglas Alderson’s Dorset A7 Club advice here and Roy Goodrum’s (Essex A7 Club) here. With aid of these excellent sets of instructions, I attempted to repair a non-functioning PA which I found had just two ballbearings out of the required 30. Also note:

  1. The speedo pointer is noted as needing a pry bar for removal. I found that the pry end of some pincers worked, with a finger over the pointer.
  2. You will get away with a standard small kit screwdriver for removing the 3 face screws IF you thin its end with a diamond pad or similar. The brass screws are not that small, but have a very narrow slot.
  3. It is essential to unscrew the retaining set screw for the top brass bearing before removing. It will come out with effort if you forget, but you will entirely ruin the thread, making re-assembly very difficult. Do not ask how I know this.
  4. Watch for other washers or added springs that might have been added in the recent past. I ended up with one that was not required, from past bodgery.
  5. The ballbearings are available from David Cochrane A7 Components and also from ebay. Mine were magnetic and thus metal pointed tweezers were helpful initially, but when the grease stage is reached, a wooden cocktail stick helps when they get unruly.
dav
cleaning the lower ball race after removing the central piece below
dav
greasing the ball race to stick in the 15 ball bearings. Use less, otherwise they get lost in the goo…
dav
seating the central piece in the lower race; this is gravity assisted until it comes to wanting to get the same gravity assistance for keeping ’em in the upper seat…
dav
WARNING – this is what will happen if you don’t undo the locking set screw on the top before removing the brass top – thread damage! I used the end of a small flat file of the right sort of dimensions to unscrew the ‘plug’, turning it v.carefully to avoid bending the bobbly bit which sticks up through it as you remove/replace it
top ball race ready for cleaning
dav
working directly over a big clean tray essential… and they don’t bounce when they have grease on 
dav
a better amount of grease
dav
the difficult bit – holding the central section upward to maintain pressure on the lower ball race (the whole speedo is presently upside down) whilst re-threading the brass upper race until the end float is just right. In practice, I found that the ball bearings jumped out a lot, but that you can spin the core to thin the grease to check whether you have gaps. I tightened the brass piece until it just locked movement, then edged it back until it was spinning freely but safely retaining all the ball bearings. 
dav
This clipped washer was present in my speedo but I’m guessing that it was a past bodge; let me know if you find one as I might need to find out what it does!
sdr
cleaning dials with a bit of WD40

Please share any other advice not contained in these three reports above, by commenting on this post.

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