Want to keep the bike original so really need that original coil that my be out there. Clear fiberglass looking on the outside. Thanks
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Need an original coil for my 1967 Triumph t 120 TT
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You have two things going against you: the effect of solder flux on the fine wire of the secondary, and the long-term (in)stability of epoxy resin,
Although based on limited data, I believe the high-tension side of ET coils has a fundamental defect that causes some or all of them to die of old age even when not used, which makes finding a functional coil problematic. This happened to both 3ET coils on my Triumph 500, to one of the two 3ET coils on a friend's BSA Cyclone, and to a new-old-stock 2ET that I tested. My speculation is the factory used slightly acidic flux to solder the very fine wire of the secondary (0.003" dia.) and that this slowly corrodes the wire with time. This is consistent with the fact that although the HT lead of one of my Triumph's 3ET coils had infinite dc resistance, the coil worked fine when I tested it on my Merc-o-tronic coil tester. Immediately after that test the dc resistance had the proper 5.5 kΩ, consistent with having developed a temporary conducting carbon track during the test which carried enough current to spark the tester.
The second issue is because of their chemical makeup, epoxies in general are not incredibly stable. At 50+ years, whatever epoxy Lucas used for the ET coils seems to be well past its best-buy date, with cracking and discoloration a universal problem.
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