You have a question???

 

thats why a non powervalve 1978cr250 make about 20hp and a 85 makes 50hp ?? come on dude

 

LOL!!!! 85 makes 50hp huh???????? hahahahhahahahhahahahahahah
Oh man good night!!!!!

 

How about a '81 maico 490. It didnt even have a reed valve and it is called by some the greatest open class motor ever.

 

do some research and see for yourself

 

i think he meant 1985, not an 85cc

 

yeah 1985.. sorry for any confusion

 

Here is a picture of a CR 500 engine. I can't tell if it has a powervalve or not, so take a look.

DV

 

Know how the higher your exhaust port is the more peak hp you make but the less grunt because it moves the powerband up? all a powervalve does is act like a movable roof for that port. At low rpms it drops down to give you more grunt, at high rpms it raises up to increase the hp. I think sometimes they do decrease overall top end power because they are in the way a bit but they let you run a higher roof at high rpms than you would have before because you dont have to compromise as much to keep the bottom end. In otherwords, for a pure drag motor it would be useless, for a low speed grunt motor it would be useless, for an all around motor its awesome.
The reason older models had less hp is because the ports werent as efficent, and the reason the powervalve motor probably had more power is because they were able to run a higher exhaust port for top end without sacrificing the essential bottom end. On a 500cc machine it isnt quite as essential, they are going to have torque either way.

 

Top the best of my knowledge the KX 500 was the only open class motor with a powervalve from the big 4.