I think the whole idea of the roller bearings instead of ball bearings plus the seal design is to lessen parasitic losses .You have to remember these little "Jack Russel terriers" were made to run like scalded dogs .Problem is the bearings are shorter lived before they develope side slop which takes the seals .
Before they came out with after market cylinders and piston there were dozens of crankcases on flea bay because the same P and S in OEM was half the price of a new saw .About 50 bucks would buy one and probably every one needed seals and bearings .I know I bought two to repair a couple of case leakers and of course had to replace seals and bearings on both .
On that which were done a couple of years ago I didn't press the seals in or use some special seal driver .It must have worked because mine is still doing okay and the two I did for a trimmer bud are still on the job .---more than one way to skin a cat ya know---
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