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Housing, spark slug cable complete, right hand 32000-42
Housing, spark slug cable complete, left hand 32001-42

After recreating the top-light brackets, Willem had another challenge for me. Aparrently THE most difficult XA part to find is the sparkplug cap. The spark plug caps are in a highly visible location and one can immediately see if the wrong kind have been used

The original parts were made from thin stamped steel back in 1942 and aparently have all rusted away by now and Willem had only 1 complete set, he needed 14 for his 7 XA's.

I studied the documentation and measured up the set Willem had and made CAD drawings of all the parts, plus added the original part numbers.


The reason these sparkplug caps are relatively complex is that they are radio suppressed, this was something fairly common on military (and police) vehicles. The radio suppression is achieved by added an extra layer of metal outside the insulation of all the parts. For this project I would be needing to make steel stampings, bakelite insulators, folded edges, CNC machined bits etcetera, sounded like fun!

Keep in mind that the original tooling would have been quite expensive and intended for large production numbers, whereas I intend to make 30 of these sets or so, so I would need to get a bit creative.

Part 1, Shield spark plug, lower, 32140-42


This part has 2 interesting features, first of all it has an internal hex shape that would be tricky to machine and it has 4 very thin flaps at the bottom that clamp onto the body of the sparkplug. After some experimenting and a few manual prototypes I decided CNC machining plus wire erosion for the internal hex was the best solution.

Speaking about the internal hex, the original XA spark plugs had an unusual hex size and are no longer available anywhere, so the design was slightly changed so it can be used with "normal" sparkplugs such as the HD No.3 (part number 32303-47A). After all the plan is to ride these things!



I made a special tool to bend the flaps, worked like a charm! After all the machining was done I put the parts in a vibrating drum for 24 hours with polishing soap and little stainless steel balls, this removed all the burrs and sharp edges and made the parts look and feel less brand new.

Finally they were Zincplated, as an alternative for the original Cadmium which is outlawed here in Holland because it is very bad for your health apparently. The look is very similar.

 It occured to me when the first batch was ready that maybe I should have made them in stainless steel and then glassbeaded them, after all rust was the main reason they are so hard to find now..