i was on another site and they stated by adding a cdi or rev box(i think they are the same thing) it can cause damage to the motor causing severe engine failure, i was planning for my stock 400ex, is curtis sparks x-6 pipe, K&N, sparks ignition advance key, airbox mods, rejet , and rev box, does any one know if the rev box is harmful with my mods? and is these mods besides the pipe worth it?

 

The rev box is only good if you hsve major engine work done. With a stock engine you will not notice any difference.

 

yeah but will it hurt?

 

It won't hurt you if you aren't revving it to the new limit for long periods of time. I was thinking about getting one, but for the most part...everyone I talk to says that they are junk. I did find out that the stock xr250 CDI box is the same as a white brothers rev box. You can buy the xr250 box for $72 from ServiceHonda. The degree advance keys are supposed to be good for stock motors, but nothing that has been bored out. It's only $20, so you might as well try it, and if you don't like it, take it off.

 

I had the Sparks Racing no rev limit CDI on my 250x back when it was at 273cc. I would have to keep it reved out to get anything out of it. Constantly doing this (along with junk RD springs) floated my valves and spit a keeper. $89 a piece intake valve was slammed by the piston. New guides, valves, springs, valve job, keepers, TI retainers, etc later, I went back to stock rev limit.

 

On my bike the rev box makes a huge diference. The bike has more power on the top and is more flexible. Mine is moded and it makes a dif. when it was stock i had it and noticed no change till it was moded...

 

In my opinion rev boxes are useless. By the time you get to where you stock rev limiter is even you're done making power so whats the point. Why not just shift up into another gear?

 

Because once you modify a motor it moves the powerband up in the range. You will need to shift at a higher rpm to take full advantage of the new powerband. You can't hit the right rpm with the stock rev limiter, at least on the DS [img]i/expressions/face-icon-small-smile.gif[/img]