I acquired an Echo PE 200 edger, serial# 09016715, and a SRM 210 trimmer, serial# 08308360 from a customer for some work I did for him. They were both non- runners, but appeared in good condition, used only for his modest size yard, and garage stored for several years before he gave them to me. Both units have the same engine and exhibit the same conditions. The fuel lines were deteriorated, and there was no way to test them by simply putting gas in the tank and trying to start them. They did fire and run when gas was dribbled into the carb port. A compression check revealed only 90 psi for each unit. 110 psi or higher has always been my preferred number. The tester has a schrader vale in the tip, and has proven reliable in past use. An inspection through the exhaust port showed heavy carbon deposits on the top of the cylinders and around rings for both units, but no scoring. I concluded that the rings were sticking, and that new rings would increase the compression. After cleaning the carbon from the pistons, installing new rings, and cleaning the cylinders; compression for both units is still 90 psi. Once again, no sign of scoring on the pistons or cylinders. Both units fire and run when gas is dribbled into the carb port. Is 90 psi compression adequate for these units? I would like to know before I spend any more time or money on them. Thanks in advance.