for the price of a re-bore, piston/ring kit, gasket set, you can get an aftermarket cylinder kit complete. If the compression is that low I would carefully inspect the lower end for wear. It dosen't sound like you are to "into" tearing it down yourself, so I would think $400.00-$600.00 US would cover a rebuild at a good shop. With all the correct parts a re-build should take 3-4 hours. There may be a shop local to you that will take a core on your engine, and supply a rebuilt to you. Then again if ALL else is good it should only take about an hour or so to change the piston/rings, about $50.00. Is yours 2stroke or 4?