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My money would be on the starter still being the cause. Removing it and spinning it with zero resistance dosnt really say its good. But before i was 100% i would check the idler gears and bearings in the side case that make the connection to the starter clutch gear. Since you changed that already my money is still the starter though. My .02
My money would be on the starter still being the cause. Removing it and spinning it with zero resistance dosnt really say its good. But before i was 100% i would check the idler gears and bearings in the side case that make the connection to the starter clutch gear. Since you changed that already my money is still the starter though. My .02