A lot of the inexplicable rattles mine has developed at the rear end have been down to small stones and gravel getting into the hollow swingarm through the big holes in each side after doing faster gravel forest trails and fire roads. I also live a mile down an unmade road, which also doesn't help. You'll probably be surprised how much crap you can pull out of there!

I periodically have to empty the undertray on the car for exactly the same reason (about once a year) when the rattling gets too annoying to live with.

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