One had one cam the other has two...
Seriously, its a ford chevy thing, Go to honda motorcyles site na look at the CRF450 site, they give an interesting reason why their "uni-cam" design is good. It sheds some light on the subject.

 

you can make a better flowing head with DOHC.

 

Yup, DOHC means less moving mass, better valve alignment, higher rpms, more vrooom vrooom....

 

DOHC usually means the valves are more difficult to adjust too. more moving mass high on the engine.
SOHC usually adjust the valves on the cam followers, and in some cases, like cars, you can get different ratios for the rockers to change the lift, i.e., the openin length of the valve,, but thats too techy for me..

I dont see a significant difference in the 2 designs.. they both have their good points. [img]i/expressions/face-icon-small-wink.gif[/img]