| This a very common problem on STs (and presumably Monsters with the same arrangement). After adjusting the chain and torqueing the axle nuts it is essential that you tighten the adjuster bolts. If they are not tightened properly (8Nm) they can come loose and get mangled in the sprocket or on the RH side of ABS models can chew up the ABS sensor rotor. There are quite lot of postings about this on US sites, with many owners lockwiring them, but like Jools I just make sure that mine are tight when I lube the chain. | 
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