cdi mod for your 400ex

[raptor660103]

I am sure some of you this but I just thought I would pass this on.
Many aftermarket CDI boxes sold for the 400EX are actually stock Honda XR250R boxes. The unmodified XR250 box will give you about 800 more rpm on top and a faster ignition curve. You can purchase this directly from your local Honda dealer and save money.
Order: CDI for Honda XR 250 1992-2004
Part #30410-KCE-671

[CJM]

Interesting, how does the EX respond to the 250r box besides 800rpm more?

[raptor660103]

it will make more spark which meens better fuel burn insult meens more power now im not saying it will give u 10 more horse but it is noticeable. it will also give u a little better throttle responce.

[CJM]

Originally posted by raptor660103
it will make more spark which meens better fuel burn insult meens more power now im not saying it will give u 10 more horse but it is noticeable. it will also give u a little better throttle responce.

Seems worth it, it plugs right in?

[honda400ex2003]

yeah it does, steve

[CJM]

Cool, ill put it on thelong list.

[bkelley]

I'm not sure they're any cheaper than the "aftermarket" CDIs listed for the 400EX. I just checked DGY and they sell the XR250 CDI for $100. And they are considerably cheaper than most OEM part stores. You can get the AMR Stage 3 CDI for like $80 on eBay. I still don't believe CDIs are worth the money, anyways.

[sc400ex_rider]

350x plugs in and has no limit!!!!! but yes there overrated. i like my stock cdi just to be safe. ppl put them on, rev the piss out of it and drop valves. :confused:

[JOHNDOE83]

Did you guy's know that you can actually use almost "ANY" cdi box.

Really, all you do is re-wire it to your application.

90% of scooter's and chinese atv's have the same wiring and plug's as a 400ex also, the timing curve and sometimes rev limit is decreased alot in these box's but some do work.

We once used a kawasaki sportbike coil and cdi on a 1984 suzuki lt250ef atv. It really didnt make any difference on performance with that atv, but did work really well.

[raptor660103]

it will make more spark which meens better fuel burn insult meens more power now im not saying it will give u 10 more horse but it is noticeable. it will also give u a little better throttle responce.

[MidnightBlade]

threw around getting a dynatek adjustable rev box but i dont have the cash right now. :confused: not sure whether to save up and get it or get something different. advance keys are out of the question. most likely going to get a monster coil though, not sure how much they are used compared to new but ill find something.

[bherriman]

look at any dyno chart on a 400ex they stop making power ever before the stock rev limit ( 9100 I believe) so why buy an aftermarket box to make it rev to 10 grand if its not making power anymore? just putting more stress on the valve train if you ask me...buy a degree key instead for the throttle response

[ish416]

Originally posted by bherriman
look at any dyno chart on a 400ex they stop making power ever before the stock rev limit ( 9100 I believe) so why buy an aftermarket box to make it rev to 10 grand if its not making power anymore? just putting more stress on the valve train if you ask me...buy a degree key instead for the throttle response

Agreed, there is no need to replace the stock cdi unless you have a built engine that can continue making power at 9000+ rpm.

The majority (95%) of EX builds are good for about 8000 rpm then the power starts to sign off.

Unless you have a fully built race engine then you are basically throwing your money away.

A better way to spend your money is either a timing key or a 450R carb. Both of which will give you much better throttle response and power than a CDI.

[bkelley]

That's what I've always told people who are considering CDIs. Most of the time they've already made up their mind and just buy them anyways. I got both the Sparks key and a 450R carb for like $100. They are both well worth the time and money and will produce much better gains than a CDI.

[400exshop]

the xr25r cdi box gives you 800 more rpm's and more timing curve, but what i need to know does the 350x give more timing curver also or just more rpm's?

Thanks EJRacing

[ish416]

350X has no limiter that I am aware of. Not sure about timing advance.

What I do know is that it is useless to "upgrade" your cdi from a factory 400EX CDI as they are completely done making power by 8000 rpm. Anything more than that is more wear and tear on your valve train.

If you raise the RPM limit on a 400EX you don't know when to shift in the first place.

[400exshop]

With all the mods my bike has it dont stop pulling till it hit the limiter, so my bike could use a lil more rmp's.

also a real racer know's when and where to shift his bike becouse he can feel when the bike stops pulling.

some people think the harder you rev, the bike the faster it will go. that it not the way to ride the bike.

but i would like to say thanks for your input.

[ish416]

I forgot your EX is one of the built few that can run that rpm while still making power.

Shop you run 300ft or 1/8?

[400exshop]

we run 1/8 mile and dirt. let me ask you this ( have you ever seen a 400ex make 68hp? ) cuz mine does and i have posted the dyno sheet on here befor.

The 426 runs 7.55 all motor in the 1/8 mile and 7.10 in the 1/8 mile on nos, it will go faster on nos if i can get it to not break up at the 594 mark, at the 594 mark my son just backs out of it so we dont blow the motor.

We also drive state to state to drag race other 400 to show we have the fastest 400 in the (US.) we run 450s,raptor, and shee just to prove a point.

[Rohr397]

Kind of highjacking this thread but my Ex won't hit a limiter. It might eventually but I'd have to rev it unreasonably high. My 450r on the other hand could hit the limiter so easy I sounded like Barcia.

[ish416]

Shop, I remember seeing your dyno sheet for the EX and I think you posted one for a Raptor 700 too.

Seriously impressive for sure.

Are those times in the 1/8 dirt or asphalt?

[400exshop]

asphalt 1/8 mile. we have some video's on youtub look us up, ericcrip1 is the user name also EJRacing's 700 vs 1300 busa.