Howdy how much compression is need for a old chainsaw to start and run? why im wondering this is i do have a older Jonsered 49sp poor lil saw didnt have spark when i got her yep she was used and abused.. so cleaned it up and got it sparking again a real nice clean blue spark.. Also cleaned the carb up and then i pulled it over and over and over!! I poured a lil gas down the plug and still no go.. Seems really low in comp. when pulling it comparied to my other oldies. Any ideas or help on how to up the compression a lil with out putting new rings in her?? I think according to my wonky old compression gauge shes running at about high 80s - 90 mark.. Most of my old outboards from the 1930s era have no trouble running some on only 50- 80 pounds! strange... oh would the gas mix have anything to do with this also? all i had at the time was 50:1 which im sure is not right but should still run for a few seconds on it?? Any ideas? and thanks..