Like r_rider said, it will never run. Take the cylinder off and get it bored by a shop and have them get a piston for it too. Hopefully you can find a shop that can do it it time and get the piston in time. If you take it to someplace on monday, have them order the piston that day and try to bore it asap, you should have everything at latest friday, hopefully.
Also, riding in dunes with a 125 is a bad idea. The engine will overheat from all the stress from trying to keep it going in the sand.