Well, firts about the engine of the 12v NT dax.
It's the most reliable 4-stroke engine ever built.
Really, if you keep it original it is bullet proof.
The downside of this reliability is indeed the decreased power and torque.
Concerning the electrics, if you want a maintance-free bike, do the 12v CDI conversion.
If you are even only a bit of a technician, keep the original 6v ignition system.
The spare parts are cheaper, there are less of electrical parts (which can all break down) in the wire loom, it's faster as a solid 12v ignition CDI system (when set up right) and most of all, it's original Honda '70s technique!
And that's one reason why we do love the charm of these bikes.
The front forks, the oil NT forks are indeed a lot stronger and comfortable.
But... more complicated to keep it on the road under rough conditions, and the design is a big downside (to my eyes).
I completely agree with you that the plastic NT parts do not belong on bikes like ours.
As for the seat cover, I payed somewhat like 130£, shipping included.
Too much? Well, it was worth it for me, so no regrets. The replica cover (the only one with Honda on it) costed 130£ as well, and didn't fit the bike at all. (Nor the shape, nor the fabric, nor the print)
And I'm sure, if I ever end up selling it, I'll manage to make a good profit out of it.
So my thoughts? Honda OT dax looks all the way!
And if you want to ride an oldtimer, the electrical or mechanical issues will always be a part of the charm!
If that's not what you like, you might as well buy a brand new plastic scooter.
