Steve,
There is a bit of brute force required to get the shaft to slip back into the yoke. I generally use a rubber hammer to knock it in, but check first to make sure the end of the splined section is started in the yoke and will slide straight back in when coerced in.
I just fetched my old driveshaft to get some photos for you in regard to your first question about it
Hopefully, the photo is clear enough to see the state of the splined sections
The end with the circlip has no wear whatsoever on it, most probably due to the fact that it's locked in position in the universal joint, as opposed to the back end....
^file photo
where the splines slide fore and aft in the diff yoke.
I'd say that Jonesey is right on the mark with his reply, and that Yamaha designed it like this so any wear (like mine) will be concentrated where it's less critical, whereas if the front spline got worn like this, I'd hate to imagine the vibration from all the slack in the U joint, especially at speed.
BTW,
That driveshaft of mine is the culmination of years of improper maintenance, use of the wrong type of grease, and over 300,000 klms of worry free riding.
Just make sure to give your splines a nice coating of a quality MOLY grease before fitment, and you'll be right as rain.
