Rev or CDI boxes?

[Helix]

Are all rev boxes the same? Do they make that big of a difference? I've been shopping around looking at different rev boxes and looking at different sig's on here. But I thought I would check here first before I made a purchase. I can get a big gun rev box for like, $90.00. But I don't know if thats any good or not.

[00.400ex#55]

i bought a big gun. its not worth it. a freind switched his stock one with mine and i didnt even notice untill he told me. plus they definatly are a pain in the *** to get the motor started. i ended up bump starting it on the trails alot, sounded like the battery kept dying, but it wasent.

[Helix]

Yeah, I'm probably not going to go with a big gun rev box. I see a lot of people on here that have a White Bros. rev box. I still don't know which one is best.

[gcart2]

isnt the point of a cdi just to giv you 1000 extra rpms? why would you need that on a air cooled 397cc engine? unless its built to the core theres no point for it. think about it... whats 1000 extra gonna do:confused: JMO:ermm:

[Helix]

Not sure what it would do. Thats what I'm trying to find out. I've been riding with a yfz 450 all weekend and my 400 just feels like it revs out to fast. Did know if a rev box would help or not.

[dobbewancanobe]

No. It is just to keep you out of the rev limiter. not that you were ever in the rev limiter.... If you are than you need to shift. I will never use a cdi on my machine. No more power comes from 1000 rpms in that engine. just my opinion.

[Big - D Racing]

FACT: Stock 400ex hit there peak hp in any gear around 7200 rpm then slowly die off. What that means if you are trying to get the full potential out of your motor you should be shifting at no more than 7400 rpm. To keep the hp up and your quad at it's top potential. If you are hitting your revlimiter which is 9000 I believe. You are not shifting correctly at all. And you are actually causing your quad to produce less hp. Take a look at any dyno and notice where the peak hp is made and then how quick it dies off. I.E if you go beyond that peak rpm your hp goes down! Therefore there is absolutely no need for an aftermarket cdi that increases your rev limiter by 1000 rpms. Anyone who rides there motor out to there has no clue how to ride, and is doing more engine damage that anything.

Now if you have a fully built 400 than it may be worth it. My quad is a fully built 440 that outruns most 440's out there. I have a duncan national 440 with the powercylinder, oversized valves and one of the most aggressive cams on the market Web 463/9i cam. Than also ported polished. Hell read my signature line. I have experienced with all cdi including white bros. (which is a stock xr250), big gun, sparks, dyna programmable (which was good but didn't last the cdi would always fry itself). I had that one 3 times I kept sending it back to dyna. Piece of crap. And now the Procom. The procom by far is my favorite! 1 it doesn't mess with the timing like others which is part of the reason you have problems starting your bike with other cdi's. It does one thing and increases your rev limit. And the price is only $45! You can get it here: http://www.procomengineering.com/

It is by far the best and I have played around with them all! I have had now for a full season with no problems or complaints. My quad starts everytime as easy as when it was brand new. You however I wouldn't spend the money until you are ready to build your engine like mine. It will do more damage to your engine than anything if you actually take the rpm's that high. Plus you lose power!

[XXXRACER165]

Hey Big-D how much hp your engine pumping out?

[Big - D Racing]

I'm not positive I haven't dynoed it with the new cylinder and cam. I had it dynoed before at 42hp with a lower compression piston, stock cylinder sleeved to 440, web cam's 450/451 cam, and a mild port and polish. Now it has an aggressive port and polish oversized valves, the 463 cam, the duncan power cylinder 4000, custom intake. It is defnitely a lot faster. If I had to guess I am pushing 50hp. Not positive though I need to get it dynoed.

[XXXRACER165]

Cause I'm pushin' 42hp too. Same setup as yours just I have a different cam (Hot Cam Stage-2) and a White Bros Pro meg exhaust.

[Helix]

Wooo! Bet that thing hauls!!

[XXXRACER165]

Originally posted by Helix
Wooo! Bet that thing hauls!!


It kicked my dad's 450R in the booty before he cried (I WANT MORE POWER)! And installed the HRC kit in it.