Ok so I will admit that this one was my fault as the sled ideled for 45 minutes as we were trying to get my buddy's ski-doo running. When we took off it ran fine for 4 miles and the started backfiring. Loaded it up and went home to check the compression and it was 120(PTO) 120(Center) 27(Mag). After this I took out the scope and checked the piston and there was a huge hole in it. I have never redone a viper so I was wondering if you guys think I should redo the whole motor or just the one piston and sleeve. Or should I redo all the pistons and just the one sleeve? Also is there anything else I should check? Also does anyone have a good site to order this stuff from as I want to get back on the trail soon? Thanks