xr250 cdi box?

[Danimal]

Can some one tell me what year xr250 cdi box fits a 400ex?:huh

[Tommy 17]

what does this do to the 400ex is it a good mod how much it cost.

[Deathbringer]

It changes the stock rev limit of 9300rpm to 10400 I believe. People found out the the WB rev limiter changed the rev limit to 10300 and moved the timing forward 5 degrees and costs around $110. You can do almost the same thing with the XR250 cdi box and for about $60-70. Sorry I don't have the year in front of me. Hope that helps

[Drtridr18]

Does the XR rev box advance the timing also? Is it worth the savings if it doesn't??

[Deathbringer]

Yes.

10400 and 5 degree advance. If you can find one, it will save you a ton of money.

[Lil90man!!]

Hey you guys i always hear about a higher rev limiter for a 400 do they make them for a 300ex??? and if so which one would u suggest?

[beerock]

whatyear xr250r cdi box should you buy?

[Adams44]

Hey BEEROCK;
The XR250 CDI unit I believe is a 2000. This box DOES NOT advance timing, nor does any of the other boxes. It simply increases the maximum RPM before the CDI starts cutting out the spark. I have seen numerous posts on these boxes advancing timing. I called HONDA tech line and a couple of big time motor builders and they verified that it doesn't advance.

To advance the timing, you need to relocate the either the flywheel or the detector of the flywheel and you can buy those from Sparks, TMM, TC, GT Thunder for about $15.

Advancing the timing will allow the motor to rev out easier, which will require a higher max RPM cutoff point. That is why these two mods work together.

One thing to consider, what RPM range does your motor make the most power, if it is under 9000 RPM, then you should shift before you reach 9000 RPM and then a CDI unit doesn't do anything for you.

If you have a highly modded motor that is still making good power high in the RPM range, then go for it. It is a cheap mod too, so that is one nice feature.

Good Luck, hope this helps.

Nick
426EX

[beerock]

thanks for clearing that up, I know to much advance is bad for a motor.
I think with the cdi box,xr400 cam and a bigger carb is the best way to boost performance for a stock bore size 400ex,...... that already has an intkake and complete exhaust, of course

[barbwire44]

The 1996 xr250r cdi is the box that is being used on the 400ex it is the same box white bros. is selling for over 100.00 bucks. Fair warning on the box is that it will damage youre engine in the long run. The bike will actually be predetonating and will start blowing head gaskets, But the head gaskets aren't the problem, the problem is the studs are actually starting to pull. Talked to a very well known engine builder who said to put it simply 400ex motor cannot take the high rpm. And went on to say even a highly modded ex cant handle the rpm either. So im stickin with him on this one, besides the power curve on the bike drops off well before 9000 rpm just look at the dyno's.:D

[beerock]

hm so the best thing to do is just get a xr400 cam? and then go right to the bigger carb???

[barbwire44]

I would go with the xr cam,and if youre gonna tear it down for that you might as well put in the higher compression piston for another 150 bucks the cam and the piston seem to work well together. I will be installing mine this weekend should have it broke in by friday next week from the info i've gathered most engine builders told me i can expext between 5 & 8 horse more than im getting now so i guess i'll see what happens. I bought a je 10:6.1 406 (86mm) piston and an xr400r cam and im gonna install the viton valve seals and rejet the carb so she better run good.:D

[Deathbringer]

ADAMS44

I did a little more research and I stand corrected the box only changes your RPM range.
You need an Exhaust Flange to advance the timing, most will allow you a +/- 5 degree play. This will help if you are running race fuel and stuff like that. Anyway thanks and sorry about the incorrect post.

[Drtridr18]

an exhaust flange?? what??

i thought the flywheel key was the easy way to advance ignition timing

[liltazz]

just turn the distributer counter clockwise. this will advance your timing.:D

[stocktires]

LIL90MAN,
Trinity will take out your rev limiter in your 300ex, that means no rev-limiter in the bike! You'd probably have to be kinda careful, but every engine builder says thas the 2nd thing to do to the motor (after exhaust). My ole 300 needs it with my fmf iv2 exhaust, at about 1/2 throttle you have to shift! but call trinity and they can do it for like around $75 i think and ask em what are the +'s & -'s!

[Lil90man!!]

well the shop right down the road does it for 70 bucks BUT alot of my little cuzins(like 7-12) come out to our house and they can't really ride very well little alone ride mi 300 with the clutch BUT "they are mi cuzn's so if they wanna ride it they can"says mi mom so there they go if that bike didn't have a rev limiter at all mi bike woulda been toast the 2 night i had it!!!!!!! so i am kinda look'n for just a higher rev cdi:) thanks n e way!!!

[stocktires]

i've never seen an aftermarket one for a 300 and i've looked ALOT of places for motor mods. I really dont believe anyone makes one. 300's arent the most popular quad so aftermarket doesnt support em a whole lot. Maybe if you put a bigger front sproket that would eliminate the rev-limiter problem! Has anyone ever though of that? But you'd need a bigger rear sproket and chain! think about it! it would be cheaper than a whole new rev-limiter and you'd have new chain and sprokets!