It's never a bad idea to have a used vehicle checked out by an independent mechanic. If the seller is buds with Ted then you may just be getting a hand-wave certification (the kid that bought my old car claims he has a buddy who will certify for him).
That said, the bike might be just fine despite this. There's always a crap-shoot element to buying a used vehicle. I'd at least take a friend along who is knowledgeable about bikes to have a look and get his opinion. For me, my level of precaution is proportional to the amount I'm spending. Which bike?
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