Join Date: Feb 2019
Thanked 6 Times in 6 Posts
This is a bit of a known issue with my "big bike", a Honda Valkyrie. It's generally thought the root cause of the spline failure between the driveshaft and final drive cup is the boot on the swingarm to the trans output shaft getting hard with age and allowing water to seep in, which then runs down the driveshaft tunnel and gets trapped. Seems much more common in more humid/rainy climates, and to a degree people that wash the bike frequently, or ride in the rain a lot. Occasionally pulling the rear drive to re-grease the splines staves this off (most shaft drive bikes do suggest greasing this occasionally in the maintenance chart, but it's widely ignored)
Anyway, the issue of getting the spline cup off is the same. No real good way to hold it, Honda says you need a special tool. It has a locking nut and is usually pretty stuck on there after 20+ years. People have a hell of a time trying to make tools, jam the drive from turning, trying to beg/borrow the special tool, ect. I haven't seen the C50 one but it sound like pretty much the same deal.
I grabbed my cordless Matco 1/2" impact (which rocks, it makes my air powered one feel anemic) and it blasted the nut loose in about half a second, no holding the drive needed. The cup then slides right off. Same to re-install. The torque spec to re-install is approximately two ugga-duggas.