i have a 400ex with a duncan full exhaust. i was thinkg of getting a cdi rev limiter pill wich raises the limit by 1000 rpm. anyone have expierence with these? can the bottom end of a stock 400 take the extra rpms?

 

If you look at the torque and horsepower curve of the 400ex motor, going an extra 1000 wont help a thing. The power drops way off after 7000 rpm, and by the time it hits the stock rev limiter, its down about 7 hp from peak. Unless you do some serious mods, and change the cam, the rev limiter wont help a thing. Changeing to the better pipe isnt enough. In fact, the aftermarket cdi usually arent as reliable as stock, and some even have hard starting issues, if the battery voltage drops too far.



The red line is a modified 416 motor, and the blue line is stock.

 

im using an amr rexbox and i think it helped alot

 

Will the stock bottom end on a 400 motor hold the extra 1000 rpm. I plan to go with a bigger bore and higher comp. with the same stroke (stock crank).

 

no one knows? opinions?