I found a company in England who repairs the splines on the K-bike drive shaft. They will cut your spline and weld a new one. You have to send them your old shaft, and they will send you a rebuilt. Carriage to the USA/Canada by insured air mail 22.50GBP. The repair is 60.00GBP so the total would be 82.50GBP.
If you prefer to repair the shaft on your own, they will supply the spline but you would have to agree to relinquish any claim against them if the shaft is not serviceable after you have fitted it.
You must NOT machine the drive shaft to make the insert a good fit, you must machine the insert to make the fit. The part no is #55552 @ 38.50GBP 3.50GBP postage = 42.00GBP total. The insert is welded into final position and can only be used on 1986 on 20 tooth splines.For more information, contact: