Need help. 1998 polaris 400 sportsman.

Whats up guys. I have a 98 polaris sportsman 400. 2 stroke. Owned it for a very long time now. Died last season. Compression tested this spring. 25 psi. Pulled top end and replaced. New piston. Rings. And gaskets. Reinstalled. Ran like shit. Checked compression again. 75psi. Believe rings are in the correct orientation. What else could I be missing. Head studs were torqued cross pattern to 28 ft lb. What am I overlooking. Cylinder itself looked surprisingly good but didnt mic it out.