[ejcycles]

Well it's like this...They are all Over Head Valve engines.

There are Push-rod engines and OHC {Over Head Cam} engines.

The pushrod engines have a single cam run off of gears, off the crankshaft, with two rocker arms that ride on the cam to move the push-rods, in turn the two push-rods move the upper rocker arms to open the valves.

The OHC {Over Head Cam} engine has a carrier that sits on top of the valves that holds the camshaft, and moves the rocker arms to open the valves. This engine also has a timing or camshaft chain in it that runs the cam.

The push-rod engine has more low end grunt than the {OHC} engine. Honda has for years been using a push-rod engine in their quads/4-wheelers due to this fact. They run about the same it just takes the push-rod engine a little longer to get to top speed. This is the reason that in 1964 that Honda developed the {OHC} engine for 1965 so it could reach top speeds faster for their smaller street legal bikes.
I hope this helps and remember about parts issues.

Bruce