I have a small number of these starter relays which I think may have been made by Nippon-Denso, and even after almost 50 years, they are very nearly indestructible (just ‘click’ on any image to see a larger copy). This style, with the metal clip cover, was used on Suzuki machines having electric start beginning in about 1971 through to perhaps late 1973 when they switched to having a plastic end cap and full length metal can. I suspect the same relay was used on other Japanese makes also. The only problem I have noticed with them is that the seals on the metal band fail: basically the two original rubber o-rings perish with age which can allow water to get into the relay. It took me a while, but I finally figured out that watch case o-rings are a nice fit as they are very small in the cord diameter, and they are as cheap as chips. I bought a package of 20 for $4 plus shipping ! The hardest part is then getting that metal cover to latch, as compressing the new rubber o-rings was more than I could manage with just finger pressure, so I assume that the factory must have used a tool to do this.
The other day I happened to be in Princess Auto just browsing the aisles as you do. Princess Auto here in Canada is something like a Halfords in the UK or a Harbor (their spelling – not mine) Freight in the USA. It is possibly the only place I’ve been to where you see men wandering up and down the aisles just looking at things, in much the same way you see women wandering around in a shopping mall. So as I myself was wandering around looking, I noticed they had some sheet metal clamping pliers on sale at half price that, with a bit of modification, looked like they’d be perfect for pulling the starter relay ring tight enough for it to latch.
Once home, I sliced a slot in the lower jaw so that the top of the clip would clear the jaw, but so that both sides of the clip could be caught. There should be a photo around here somewhere showing the slot, and also a photo of me using it on the clip just prior to latching it over the rolled retainer.
I may look at having the starter relay cases bright zinced but for now I’m OK with how they look and with the new o-rings in place they are now at least water-tight again which was the objective. As well, I’m not sure whether the re-zincing process might not take some of the spring out of the cover ring, which may not be a good thing. Re-zincing the cases would also destroy the few remaining examples that I have still having a factory decal. This is a foil label with a B, S and M on them marking the battery, switched lead and motor connections. If you think that sounds like over-obsessiveness, you are correct: it is ! But it makes me smile and at the end of the day that really is all that matters.