http://vf750fd.com/blurbs/brochures/...cb250_3501.jpg
In 1964 the CB250/CB350 both have an OHC

http://vf750fd.com/blurbs/brochures/.../cb250-350.jpg 1968

I see that Johnnypag has a 270cc version and claim it is a DOHC?
http://www.johnnypag.com/motorcycles...er300Specs.pdf

I could be wrong but it does not look like a DOHC
http://www.johnnypag.com/motorcycles...ngineParts.pdf

They also have it rated at 23.8HP and Lifeng rates the 350 at that same HP?

I do not think the CB250 was ever less then 249cc but the CB350 was only 325cc….the lifeng 350 is 320cc

I think that the JP is actually 320cc and they lied to the EPA that it is 270cc so they could get it in as a Class II under 270cc engine.