cdi boxes

[fmf400ex03]

i want a cdi box and i was wouldering wich one will have the best out put and wont harm my machine to much thanx

[Narly R]

Rocky Mountain has Big Gun rev boxes, and White Bros. They are on pg. 393. I havent ever had any experiances with either, but I think these are what most people use for slightly moddes ex's.

[nathanm82]

I sold honda parts for 4yrs now and I prefer the xr 400 cdi box it is the same as white bros but cheaper

[fmf400ex03]

i heard some thin about a gt thunder some said its suposed to be sick dont really know

a cdi box doesnt add performance...only lets you take advantage of a higher reving power bike...like an FCR carbed bike that revs out fast on the stock cdi...u may want a aftermarket so you can bring it to its full potential...i put it on my bike and it didnt even start...put the stock back in and it started right up...i may have to buy a battery charger or somethin :(

IMO these are a waste of money unless you have a modded engine....with these, (i dont know why they do this?) you better hope your battery is always full or it wont start at all...I'd spend your money on something more usefuil ;)

[nathanm82]

I think the after market ones all have some kind of trouble with starting wb bros always seem to be a pain on cold starts but if you start the quad and run it awhile and then switch they worked great. huge pain though thats why I push the factory honda xr 400 one more than anything else.

Originally posted by nathanm82
I think the after market ones all have some kind of trouble with starting wb bros always seem to be a pain on cold starts but if you start the quad and run it awhile and then switch they worked great. huge pain though thats why I push the factory honda xr 400 one more than anything else.

its because they change your ignition advance and your power curve...if you have an aftermarket battery or a battery tendor(sp) then you should be fine

[cals400ex]

Originally posted by Jumbo747
IMO these are a waste of money unless you have a modded engine....with these, (i dont know why they do this?) you better hope your battery is always full or it wont start at all...I'd spend your money on something more usefuil ;)

i agree. on a stock bike, you won't notice much if anything. my friend put one on his stock bike and it seemed like he could ever so slightly pull on exact top end when compared to my bike. it was well less than 1 mph though. however, once you build your motor, i wouldn't run without one. i hit my stock rev limiter right when my bike wants to go. maybe the 406 just likes to rev high. i would be willing to sell my curtis sparks rev box if anyone is interested. i had it on my bike for probally 8 to 10 tanks of fuel. my bike just starts easier with the stock box on.

[abcracing]

GT THUNDER does make the best cdi box on the market.wb and big gun have alot of problems starting when its cold outside.with the GT THUNDER cdi box it will start no matter what the temp is.also on a dyno run u will see a small increase in mid range power with the GT THUNDER box.it is only like .20 of 1 hp but it is an increase.you can purchase these at www.gtthunder.com or we carry them. later BILL

[hondafox440]

Originally posted by XxHonda_RacerxX
a cdi box doesnt add performance...only lets you take advantage of a higher reving power bike...like an FCR carbed bike that revs out fast on the stock cdi...u may want a aftermarket so you can bring it to its full potential...i put it on my bike and it didnt even start...put the stock back in and it started right up...i may have to buy a battery charger or somethin :(

Actually, a new CDI can add power because it changes the ignition curve. This being said, actual gains are minimal, and it acts more like adding a new pipe/silencer. It basically moves the power around. You may sacrifice some top end for greater bottom end power and torque.

Originally posted by abcracing
GT THUNDER does make the best cdi box on the market.wb and big gun have alot of problems starting when its cold outside.with the GT THUNDER cdi box it will start no matter what the temp is.also on a dyno run u will see a small increase in mid range power with the GT THUNDER box.it is only like .20 of 1 hp but it is an increase.you can purchase these at www.gtthunder.com or we carry them. later BILL


No offence Bill...:D

[400exBro]

how much does the GT rev box cost??

TC racing is 143 and Tom told me that it will start no matter what and increase the rev limiter...
i hope the GT one is cheapier...

Originally posted by 400exBro
how much does the GT rev box cost??

TC racing is 143 and Tom told me that it will start no matter what and increase the rev limiter...
i hope the GT one is cheapier...

I think they run about $125 or so.

[400grl]

I had a White Bros CDI box for my 440 - never had a problem starting - my quad always started first try even in the winter.......I wouldn't waste the money on a stock engine, though...

[norcalatver]

Go to Gt Thunders web site and look at the 400EX dyno runs. Even the highly modified ones with the rev box die out at no more than 8,000 rpm. The 473 he dynoed (gthunder.com) flat fell off after 9,000 rpm. I don't understand why these boxes are being pushed if there is no power to be made at the rpm's they're allowing the engine to go? If you are hitting your stock rev limit, you should've shifted a long time ago!

[cals400ex]

in a drag race with my bike, a rev box does make a nice differnce. i gain about 5 bike lengths by the time i hit 5th gear when racing the same bike when using the aftermarket box vs the stock box. i think that the larger bores won't need the rev box as much since more torque is produced and they don't rev as high. i run a 406 and it revs well past the stock rev limit. it seems right before the stock rev limit is where it starts to move good. the larger bores (440 and larger) may not need the box, but i know mine helps in a drag.

[norcalatver]

I don't know how to post a dyno run from another site but look at GTthunders site and look really closely to the stock cdi vs aftermarket cdi comparison. There might be 1/2 h.p difference at around 7,000 rpm. Then the after market where it peaks drops off to barely 22h.p. If you believe GTthunder then how can you possibly believe an after market box helps?:confused: :confused: Lazarus is showing facts on paper, not seat of the pants.

[cals400ex]

Originally posted by norcalatver
I don't know how to post a dyno run from another site but look at GTthunders site and look really closely to the stock cdi vs aftermarket cdi comparison. There might be 1/2 h.p difference at around 7,000 rpm. Then the after market where it peaks drops off to barely 22h.p. If you believe GTthunder then how can you possibly believe an after market box helps?:confused: :confused: Lazarus is showing facts on paper, not seat of the pants.


i understand what your saying. however, it isn't always the best to shift into the next gear at exactly the peak power. if you stay in gear longer, your rpm's won't drop as much when you are actually in the next gear. this may be more beneficial than shifting at the peak power point. this is the case for me. am i making sense? sorry if it sounds confusing.