Ok, i have two questions, first what is a powervalve motor (2strokes)? Last question, what is done to a crank when it is trued and welded? thanks for the help.

 

A powervalve is a small mechanical device that will open your exhaust port more when the engine is above a certain RPM. This creates more horsepower. Most dirtbikes 80cc and up have had them in different forms for the past 10 years or more.

 

Trueing a crank means making sure it dosent wobble when it spins by making sure the crank webs are centered right. For a lil more on Adams definition, a powervalve blocks the top part of the exhaust port during low rpms. That gives you lots of low end grunt, hit high rpms and it opens the port up for top end power. It has about the same effect as vtec or variable valve time in a car.

 

I've never seen one of these out of an engine but, I would have explained it differently. . .

A powervalve closes the exhaust port more at lower RPM's to create more compression and low end torque. Two strokes are not known for torque but, the PowerValve adds low end grunt (still nothing compared to a 4-stroke.)

At Wide Open Throttle (WOT) the valve is wide open letting the porting in the engine do all the work.

Eddie Sanders Racing probably has some info on them.