Originally Posted By: MrMeeks
Recently purchased a poulan pro 42cc chainsaw on ebay.With low compression it would not start on 40:1. Using pennzoil MP at 16:1 sealed the loose piston and the saw starts easily and with more power than the 'wildthing'.Continuing to use the saber 80:1 in the bolens trimmer with good results
If available, put in a set of over-sized rings. Compression will come up and power will be much better. It's pretty easy to pull the cylinder off a chain saw. If you know the specs, you take some measurements to see if the piston is worn. Chances are that the engine has a chrome bore, so the cylinder should be good. A little work and a few buck will give you a saw that runs like new.