rev box

[quad_man08]

is it ok to put a rev box on when my quad is stock or is it better to get some engine upgrades before thanx

[AbnMP13]

What kind of quad?

You gonna get about a 50/50 opinion on this one.

[quad_man08]

'99 400ex

[BOOSTED2V]

I had a White Brothers rev box on my 00' 400ex with just a WB e-series slip on and a filter for about 1-1/2 yrs with no issues...

[AbnMP13]

I got a White Brothers on the way, won it on eBay for $34 shipped.

Originally posted by AbnMP13
I got a White Brothers on the way, won it on eBay for $34 shipped.

you wasted your money...

here it goes...

the rev kit is actually a cdi unit from a honda 250 dirtbike(xr2509 but don't remember fro sure). there lies the problem. as i have posted many times, the rev kit has a circuit in it the prevent the sprk plug from firing if the rpms do not reach a certain level. this level is just above the starting rpms of the 400ex.

just as an example, not sure if these is the actual values. we'll say that the anti-kickback circuit on the rev kit is 1400 rpm and the 40ex starts at 1500 rpm.
so lets say that you are trying to start you bike and it only reaches 1350 rpm because it is colder, the battery is not 100%, your oil is a little heavy, your gas may need to be refreshed or a higher octane...whatever...the plug don't fire and keeps not firing as you keep trying to start the machine...what happens? you kill a battery. i killed one that was about dead, a brand new battery and a slightly used battery in one day before i found this out.

now will you see any difference? no...where do you gain the extra rpm? at full throttle after the ex is not making power anymore...how often are you running at w.o.t. for any period of time? not very...do you ever hit the rev limiter in any gear but 5th...not really...

my friend had one on his 400ex. we ran down the trail at w.o.t. for a while...i was pulling away...i was still on the stock cdi...equal riders, pretty equal weight, equal mods...again, i was pulling away...

[AbnMP13]

Originally posted by speedyquad
you wasted your money...

here it goes...

the rev kit is actually a cdi unit from a honda 250 dirtbike(xr2509 but don't remember fro sure). there lies the problem.

So Big Gun and White Brothers (just to name a few) should be majority stock holders in Honda then right? I would think they sell a few thousand of those Honda 250 dirtbike CDI's each year.

You as well as I know that there could be a billion reasons that you beat him in the race other than the CDI.

[BOOSTED2V]

Interesting... but I felt a difference from mine so???? I even clocked it as far as MPH and picked up some more MPH's so... Maybe his wasn't working properly I dunno...

Not to start an argument but why in the "H" would people market and manufacture this product if it didn't work or live up to what the articles and tests say it can and will do??? It would be false advertisement...

[blown331]

what ive come to conclusion is...

a lot of people only think of cdi's in 5th gear at "max rpm"

well think about it, you have 4 other gears that the cdi will improve the amount of rpm the bike will pull

also, as ive read, it should adjust the spark curve as well?

if that is true i can understand why its making more torque throughout the rpm range. now if the bike is geared low and stock and can pull the extra rpm it may help acceleration

but to get the best out of this im quite sure you would want other mods first so your bike doesnt run out of steam on the top end

[BOOSTED2V]

Originally posted by blown331
what ive come to conclusion is...

a lot of people only think of cdi's in 5th gear at "max rpm"

well think about it, you have 4 other gears that the cdi will improve the amount of rpm the bike will pull

also, as ive read, it should adjust the spark curve as well?

if that is true i can understand why its making more torque throughout the rpm range. now if the bike is geared low and stock and can pull the extra rpm it may help acceleration

but to get the best out of this im quite sure you would want other mods first so your bike doesnt run out of steam on the top end

EXACTLY!!! Like a pipe, filter, and Jet kit...

Now if you have a built motor with upgraded valve train to withstand the high revs... Big Gun makes a rev box that has no rev limit so you could dyno tune your quad with the right mods to handle RPM's to really scream!

The rev kits also advance the timing all across the board by about 5 degrees... So you throw more air and fuel at that and your in business.

They wouldn't sell something that didn't work... CASE CLOSED!

Originally posted by AbnMP13
So Big Gun and White Brothers (just to name a few) should be majority stock holders in Honda then right? I would think they sell a few thousand of those Honda 250 dirtbike CDI's each year.

You as well as I know that there could be a billion reasons that you beat him in the race other than the CDI.
do some research...you will find out that i am right about it being from an xr250...
what are the reasons...the only differnece in the bikes was that i have a big gun full race exhaust and he had a wb full e-series exhuast with more discs to add top end...there was a very long area where we could top out and hold that for a few miles...old road no longer used, and unfortunately, no longer available. he reached top speed before me and i passed him. my ex was a 2000 and his was 2002. everything else was stock...

read this reply froma yahoo group...it was in response to a post i put up there when i had the troubles...

Lose the WB rev kit.

The CDI box comes from an XR250 kick start bike. It's equipped with a circuit
designed to help keep the engine from "kicking back" on the rider.

What it essentially does is not fire the spark plug if the engine doesn't crank
above a certain RPM. This preset RPM level is just barely under the normal
crank speed of a 400EX... So, throw in some thick oil & cold temps, or simply
a low battery, and it's just enough to cause the engine not to start.

To verify that this is your problem you can do two things. You can put the
stock CDI box back on and see if it fires right up (it probably will), or you
can roll start it.

When I had this CDI box on mine, it was obvious. My quad normally fires off
extremely easily, but after installing the box, it wouldn't fire off when cold &
first start of the day - wouldn't even hit. If I went out and roll started it,
it would pop off cleanly like nothing was wrong.

After doing that a couple times over the course of a few days, the next time it
wouldn't start, I simply switched CDI boxes (back to the stock unit). After
cranking for what seemed like forever with the XR unit (without even a hit), the
stock CDI popped off instantly.

What it all boils down to is unless you have a highly modified engine with a
wild cam and high compression, the CDI box is not doing anything but taking a
safety net away from your engine & causing it to be difficult to start.

If you have the mods to support it, there are a few engine builders out there
that have figured out how to eliminate the rev-limiter out of the stock CDI,
which avoids using the XR250 CDI and it's anti-kickback circuit.

Gabe

---------- Original Message ----------------------------------
From: "speedyquad <chimmy@...>" <chimmy@...>
Reply-To: TRX400EX@yahoogroups.com
Date: Sat, 21 Dec 2002 18:41:35 -0000

>in october i bought a barely used 2000 400ex from my friend. this
>bike was well maintained and had less than 30 hrs on it. i got a
>good price, but it was hard to start. i played with the the needle
>setting, turned the idle down just a little, and put a new battery
>in. it fired right up every time until today. i keep it in an
>unheated garage and the outide temp is about 28. it will not start.
>i have checked the spark plug and cleaned it three or four times. it
>is not getting dirty, but wet from gas. the new battery that i put in
>started getting weak so i used the battery from my 300ex(which fired
>right up). after switching the batteries, i got a two sputters out
>of it, which i had not gotten before. i have a big gun full race
>exhaust, a k&n air filter, dynojet needle( clip set on the third
>notch from the top) i believe the 146 main jet, and a wb rev kit.
>these were all on the bike when i bought it. the only change that i
>made was to move the clip down from the second notch to the third on
>the needle. i do not want to take this to my local honda shop, but i
>will if i can't get any help here. by the way, i am in nw PA and was
>wondering if anybody else anywhere especially local has had similar
>probs.

granted, i noticed a slightly faster accelration, but not that great of a difference to deal with the starting issues i had...

[BOOSTED2V]

In brutal Chicago winter weather my quad fired up every time without any issues. No dead batteries, no nothing....

I don't know what the issue was with his quad??? I clocked my quad at 7-11 mph faster that without it and the powerband throught the gears was also improved after I put the WB box on. I don't know if some of them had a glitch or what but mine worked perfect and I would recomenned it to anyone with basic bolt ons. Thats just a first hand testimonial coming from me, the rider that performed a before and after rev box experience. But what do I know.....

[AbnMP13]

I'll hopefully get to do a before and after this weekend also, if the box makes it here in time.

[anderson3064]

Originally posted by BOOSTED2V
In brutal Chicago winter weather my quad fired up every time without any issues. No dead batteries, no nothing....

I don't know what the issue was with his quad??? I clocked my quad at 7-11 mph faster that without it and the powerband throught the gears was also improved after I put the WB box on. I don't know if some of them had a glitch or what but mine worked perfect and I would recomenned it to anyone with basic bolt ons. Thats just a first hand testimonial coming from me, the rider that performed a before and after rev box experience. But what do I know.....

im sure getting to maz rpm's may seem like you were going faster than with stock CDI but there is now way that the aftermarket CDI made your MPH,s higher, you would have to change sprockets in order to acheive this. i have been wanting to get a CDI box for my '02' but the threads on here are about 50/50 so i am not sure i want to take a chance on getting a bad one.

[GPracer2500]

I really used the extra rpms from my WB box in the dunes. Overrev can help in lots of situations. The engine had some mods but it wasn't a "highly modified engine with a wild cam and high compression". I wouldn't call a 10.8:1 416cc JE w/ a HC stg 2 highly modified. I don't dispute the deal with the anti-kickback circuitry. Nonetheless, I never had an issue starting my engine. I also kept my battery on a tender and don't live in a cold climate.

I think the starting problem of the XR250 box is sometimes overstated--JMO. It's not an issue for everybody. It just depends on factors like how much time you want to put into battery maintenance or where you live.

For me, the WB box never gave me trouble and provided a tangable benefit. For some folks the much discussed starting issues outweight all other factors. Engines that don't start when they're suppose to can ruin a day real fast :mad: . It doesn't mean an XR250 box can't work well.

[GPracer2500]

Originally posted by anderson3064
...there is now way that the aftermarket CDI made your MPH,s higher, you would have to change sprockets in order to acheive this...

Not so. If the engine can rev to a higher RPM then you can potentially go faster in each gear.

mine is kept on a sears version of a battery tender...i haven't has any problems since i took out the rev box...

[quad_man08]

ok everything youve all said dont help me lol i just want to know if its ok to put a rev box on a completely stock 400ex or will it be less reliable or what

[AbnMP13]

Go for it, I think you'll be fine. Plus you can help us solve the mystery.

Is the rev box a good mod or a "waste of money"?

[BOOSTED2V]

Well screw it... I just ordered an exhaust last night, I have a K&N and a jet kit right now. I'll order a WB rev box and I'll do a side by side comparison again. As far as overall power through the gears and powerbands and top speed.:D