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I have had an HRX217HMA for some time now & it is old (2005) but runs great. Recently picked up an HRX217K5HYAA which I believe is from 2017 or 2018. Both have the Roto-Stop clutch. While working on them, I was surprised to see that the older HMA has an fairly lightweight aluminum flywheel/fan component whereas the newer K5 has a plastic fan and a very heavy pressure washer type flywheel. Am thinking the reason for the difference is that the HMA has electric start (which I don't use) while the K5 does not. That is, maybe the lighter flywheel was required so that the electric starter could spin the engine whereas the non-electric start K5 was rope pull. Then again, the reason could be that Honda simply decided to add a heavier flywheel in later years. Anybody know?