650 like 500

[PanMan]

Hi,
I've a question. I want to buy an old Triumph but because of the law I'm not allowed to ride a bigger bike than one with a 500ccm engine after my last accident. So my question is if there are 650ccm Triumph engines which look from the outside like 500ccm engines? Like at the older Harleys at which you can't see if it's an 1000 or 1200ccm engine.
I hope somebody could help me...  

regards
Thomas