Has any one done this? Welded on a replacement spline as available from Motobins?I have a drive shaft at the engineers at the moment having the end turned off it and a new end welded on, but the engineer is a bit concerned about the heat from the welding process affecting the rubber in the end of the drive shaft. Any one have any experience doing this?

Use TIG.

In June 2001 (already 9 years ago) I inquired with Motobins about the replacement splines.
Their answer contained the following statement : "You must NOT machine the drive shaft to make the insert a good fit, you must machine the insert to make the fit."
You must cut the old splines and only clean the cut. Machining the shaft will weaken it.

Got the driveshaft back from the engineer today, looks good.

HI Robin, that looks really good, what is the final drive end like?
Looks like no damage to the rubber was suffered.
Do Motobins still do those spline kits?
Where in NZ are you? I am in Christchurch.
My K is in the garage over winter now, bugger riding in this rain!
Cheers
Stephen.

The spline on the final drive is real good. yes the spline repair piece came from Motobins. I had a local engineer machine the old end off and weld the new one on. The funny thing is, I probably will not use it, as I also bought a new drive shaft from Motobins, they are offering them at a very discounted price of 95 pounds and with the good exchange rate at the moment, that's about NZ$200 plus shipping. I will just put the rebuilt one on the shelf, it will get used one day.
I am in Woodville, up near Palmerston North.
cheers
Robin