ok, got the sprockets off, reason the balance shaft sprocket was a s*d to get off was because it had been forced round the shaft by 10 thou, notching the key slot, and stepping the key!
So, items to be replace (so far) both sprockets, and the balance shaft + of course the nuts and lock washers... getting expensive!
whilst we are on the subject of lock washers, you can see from the pic that one of the tabs on the washer is broken off... more than enough to mesh into the gears and cause all this damage..... maybe
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