The plastic valve cage inside of my sons Kawasaki Dirt Bike front fork shocks, had blown out due to over pressurization. So we made 2 new ones from 6061 Alu. First we machined the inside bores 4 different dia.'s.
Then we mounted the cage on a mandrel we made, for the outer dia.'s. The cage outer is actually tapered.
We modified the cage with 4 milled slots to reduce the internal pressure, this is a mod that the racing boy's do.
So far they are working great. Fun and complicated project.