I have a stihl ms290 cylinder with bad galling from the piston & rings . Since I purchased the ms390 engine swap replacement figured I’d experiment with cylinder honing , First I used muriatic acid soaked toilet paper stuffed into the cylinder to dissolve away as much aluminum as possible from the nikasil & it worked great but the big chunks of aluminum needed to be honed . So I used a deep socket wrapped with 3k grit wetdry sand paper & smothered it with 3k grit diamond lapping paste . Hit it with the drill for 60sec then cleaned the cylinder completely & inspected it , did another 60sec hone . Holy crap did it get it smooth & I had some nice cross hatch . Last step was 350grit diamond paste for final cross hatch. next time I’m doing 350grit first then finish with 3,000 grit for the plateau effect . I also went ahead & dropped the cylinder a bit too for more compression & ported the intake wider & a bit lower while it’s disassembled . Why not it’s a spare engine now that was once dead & brought back to life !

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