Here is evidence that you're never too old to be a plonker!

I've just been rebuilding the speedo drive on my CT1 using mostly new parts. I ordered genuine Yamaha parts and got the cable from KDI.

Everything was going swimmingly until I fitted the cable into the drive, but there was no room to fit the retaining clip over it. It then dawned on me that the 'O' ring shown in the parts diagram actually sits over the end of the cable fitment, whereas I'd initially just sat it over the bush!!   The cable came fitted with the 'O' ring, so once I removed the one sitting on the bush, the clip fitted perfectly.

You're all quite welcome for the chuckle that I've just given to you!

 

You should feel very smart.

I probably would have got out a punch and sledge hammer and tried to pound the cable end down far enough to get the clip in... and then realize... only after I broke something... that the o-ring didn't belong there.

You flatter me Mark! My first course of action was to try some gentle persuasion. When that didn't work I thought sod it, I can do without the 'O' ring - only then did I realise that I already had it fitted to the cable! 

I'd probably forget to fit an Oring if it didn't come with one & pay the price of rusting everything out over time. So ya not alone!!. Link below 'does' show #29 though & wonder if 'that one' fits in a groove where #27 arrow is pointing to seal that thingy to the brake plate. Or is it just showing it to fit in the cable groove--if cable come minus one?.
www.partzilla.com/catalog/yamaha/motorcy...1973/ct3/front-wheel

Thanks Morley and a good point. If I can summon sufficient enthusiasm to remove the bush , I might investigate it.

Na, i wouldn't disturb it. I'm not sure it does have one there--just guessing, wondering. But the Oring on the cable fitting will save any water getting past. Unless the cable casing is damaged, but new cable so all good.