JohnB. wrote:Have you tried simply unscrewing the piston to back off the spring pressure as opposed to compressing the spring? That's how the spring is typically removed on the single spring versions. If the larger spring is the same length as the spring in the single spring groups the pressure should be relieved well before the piston fully unscrews from the shaft.
Bosco uses a single 9 bar spring which gives a peak pressure of just over 8 bar, tapering down to 6 bar during the shot.
I first tried unscrewing the piston but it would not budge. I used a brake caliper unwind tool.
One of the adapters has two studs that match the two holes in the end of the piston. I was able to apply considerable torque, but the piston would not turn. I thought the spring pressure on the piston was holding it tight, so I built a jig to hold the complete group head so that I could compress the springs with the lever. Once compressed, I secured the outer spring using some stainless steel cable ties. After releasing the lever, the piston still would not turn. My next attempt will be to heat the piston, trying to expand it to help loosen it.
Any other thoughts on how to remove the inner spring would be appreciated