Had my 500cc+ Honda Ascot motor built at XR's only for road racing '500 Singles', 660 Singles' and 'Vintage Lightweight' at Willow Springs International Raceway, back in 2002/3. Man did it GO!!!!!!!!!!, and it lasted a FULL season even though I tended to over rev it time and again.
In the end I think it was overbored to almost 650!
James and Colleen Tucker.
Aut viam inveniam aut faciam
Beat our time, Los Angeles to Ushuaia 70 days