how do i go about removing the group sleeve from bosco group

You will need to fabricate something like a plunger with a diameter just less than the group inner diameter. Stephen Sweeney has posted on this in another thread here on HB. Here is the idea:

In my case, I have a two inch hole saw, where the end opposite the saw blade fits nicely with the group sleeve. I was able to position a small piece of wood over the saw blade and tap it to force the group sleeve up and out. When the sleeve was above the top of the group I was able to pull it out by hand. With some Dow 111 on the O-ring on the outer side of the sleeve, re-insertion is easy.
Also, take a look at this post: Replacing sleeve on a CMA lever (rossi group)

I'm curious to know how long the sleeve lasts. I have an old cimbali m20 lever that has no sleeve, just solid brass incorporated into the group head. I didn't realize that there even were designs with sleeves until I started to look at new machines. What is the sleeve made of? Is it stainless steel or brass? Do they eventually get scored and not seal properly with the piston seals?

It looks like brass with chrome plating on the inside:

I assume it needs to be replaced because the chrome on the inside gets pitted and water blows by the piston seals. How often do you replace it?

I'm sure Paul Pratt or someone with a lot of service experience will chime in. But my impression has always been that the piston sleeve should last the life of the machine in normal use. I think the ability to replace it is simply there in the event of damage or to get to the water jackets in the event of stoppage or other atypical problems, or to replace the O rings. I doubt you'd see appreciable wear before other parts needed replacement which are under much higher stress, like the lever pivot and pins.

The basic reason for the sleeve and body deign is ease in manufacturing and that reduces cost. The chrome plated brass will last a very long time as long as the spring does not ride on it.

bgn wrote:I assume it needs to be replaced because the chrome on the inside gets pitted and water blows by the piston seals. How often do you replace it?

I only removed the sleeve to replace o-rings. I don't think you'd get pitting unless it got scratched or has a defect in the chrome plating.

Interesting. I wonder if it's as effective at heatsinking as the solid brass group. I bought a 30 year old Cimbali lever years ago and went through piston seals twice a year. The brass in the group was pitted. The Cimbali dealer found a never used group for it and I replaced the entire group. Cost me $1000. Now my piston seals are good for a couple of years. But when they leak it rusts the spring and I have to replace the seals and the spring which is also expensive. Would love a machine with a stainless steel spring.

I have an M20 that I just finished rebuilding. These Cimbali lever groups seem to have that issue with the top seal. I have only had mine operational for a couple of weeks, so I'm basing this on research rather than experience, but I think it's due to heat destruction of that top seal which then lets water past it and destroys the springs. I have a two group so on one group I have a Cafelat silicone seal. I'm hoping this mitigates the issue. I also don't leave the machine on 24/7 - I turn it on around 10:00 pm, pull 2-3 shots in the morning and it's off by 7:30 am or so.

Sorry for the thread drift.