I have not seen a 250 two stroke quad or any of the RM, CR, YZ or KX 250s motocross engine that hits or come on the pipe at 4000 RPM...  All of the stock power valve 250 two stroke motocross engines since the mid 1980s come on the pipe or hit in the 6000 to 7000 RPM range with their peak power occurring in the 8000 to 9000 RPM range

I have never seen a well designed two stroke  where a real good pipe matched to the porting would assist the "breathing" of the engine and improve the power over more than 30% of the RPM range.


Example:

Let say the engine makes peak power at 10,000 RPM.

(.30 x 10,000) =  3000 RPM of pipe assisted performance.

This means the the power or hit would occur at approximately  (10,000 - 3000) = 7000                   

The best case scenario would be this engine hits at 7000 and peaks at 10000 with decent overrev.   

The majority of the motocross engines stock or modified seldom have a power band width that is over 26% of the RPM range where peak power occurs.

 

Example:

The engine makes peak power at 8000 Rpm

(8500 x .26) = 2210 RPM wide power band.

This means that the engine would hit at (8500 - 2210) =  6290 RPM



If we knew the RPM where the engine hit, where would the peak power occur on a state of the art engine that could have a power band the is 30% wide?

Lets say it hit at 4000 RPM, where would peak power occur in the best case scenario? 

Doing a little bit of algebra to the above equations

              the Peak power would occur  @   (4000 / .70)  =  5714 RPM