Only during off-throttle, engine-brake coasting?
Only in gear, clutch engaged?
Any gear?
The bottom part of the chain will be tight.
A chain with tight/loose spots could be skipping on the top of the swingarm, or whipping on the chainguard.
The bottom part of the engine sprocket will be pulling the output bearing rearward, instead of the top part of the engine sprocket, which normally also pulls rearward, so don't see much difference there.
Any engaged gears will have loads applied to the opposite faces, instead of driven faces. This would be dependant on which gear you're in.
Forces on the clutch basket damper springs would be reversed. Broken spring(s) could get very loose in this scenario.
Forces on the mainshaft double-row bearing (behind the clutch) would be pressing down, instead of up. Pulling the clutch lever applies rightward force on that bearing, and would change the sound of a damaged bearing.
I've refilled my
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