For those of you with big bore kits (440)

[rob-u/21]

I have a 440 duncan national kit on my ex. The people at Duncan have alway said for me to use the stock CDI, which to me makes no sense why would I do that when I can get more rpm's with the after market ones?

[Hondaluva]

IMO the 400EX doesn't make power above the stock rev limiter. Just my .02.

[Spikers400]

I agree.

[cals400ex]

that is probably best if your using stock valves or rod anyways.

[rob-u/21]

so if the ex doesnt make more power above the stock rev limiter, when I change my rev box it will make more power right?

[C41Xracer]

no you wont make any additional power it will just have more over rev.The cost of the CDI isnt worth it buy something else

[cals400ex]

all most of the rev boxes do is raise the rev limit up 1 or 2000 rpms. some advance the timing and others dont.

[Kilabanshee]

Well there right, If you have a 440 and larger cam, hotcam, webcam, white bros ect, your going to have some valve float in your head. I really dont recommend getting a aftermarket cdi, You wanna know what they really are an xr250 cdi they still have the honda parts number on the side. Mike400 told me about that soo really if you can get an xr250 cdi off service honda for cheap you might as well do that.

[rob-u/21]

thanks for the info. Ill look into the xr250 cdi's.

[nakomis0]

Most advance the timing creating better throttle response. Like said before, about 90% of em are Xr cdis.

Even if it didn't advance the timing a higher rev would still make ya faster.... imo.

[MIKE400EX]

XR250R box. Some are just reboxed, but not all though. C&D sells a good one IMO. For giggles I put my bike (sorry) in the shed for a week in January at around 5 deg.F, some nights were below 0. 15-50 oil and the original 2001 battery, 11+:1 comp., at night and VERY cold, etc...--- fired right up with the lights ON. I have to admit that I was suprised, and for once pleasantly so!!! The additional spark advance picked the bottom end power up nicely. For me it was money well spent.