ATV Florida Forum

ok my bike is 05 kfx 400.  What  cdi/rev box is the best for it?  dynatech, big gun, magnum?   Any help is greatly apriciated.   Thank  you all in advanced.




The bike is coming along really good with wrong gears i still  ran pretty quick at the drag strip in 1/8 mile  i am happy so far.

My yellow Z has a +1000 cdi and it really opened it up. I cant recall the brand but I'll look. I'm probably gonna pick one up for the grey one as well.

thanx let me no the brand if u can they make so many  its hard  to make the choice

Its an SRP +1000

i have been told by my local shop that there all made by one company just sold thru aftermarket companies.
just so you know they come from the factory bad some times. every body i have talked with has hade at least one bad one.
good luck!!!!!

get the dynatek i had one on my raptor and opened it up like crazy and you can adjust the rev limiter

thats what i herd dyntek the best one

how do u tell if u got bad one from factory?

the bike wont run right

If its not a dyna, vortex, or a yoshimura one with a mitsubishi symbol on it, then its procom which is junk.


Before you decide to raise the limiter, you should invent in some stronger valves and valve springs or you will risk blowing your motor, cupping a valve, etc...

I've had a RevMax for two years with no issues. I believe it is a Procom clone. Procoms had issues from 03~05. I believe the later models have been ok.

Should be alright, unless he's going to ride the chit out of it. Just make sure to go up in your main jet size, usually one size up. ;)

Maybe if you not running a high compression piston. What's bad about the procom are they retard your ignition timing to far which is hard a high compression engines, resulting in detonation.

I would be careful, the stock LT-Z head isn't really built to sustain the extra RPM's, if you upgrade to the DRZe springs like I did, which are dual rate, they can withstand up to 3,000 RPM's higher. Also, if you still have a stock header, I wouldn't be considering a CDI just yet, you won't gain much out of it. The stock bend of the LT-Z pipe limits the RPM range by quite a bit. It would be wise to get a full system first in conjunction with an FCR-39mm carb  before the CDI if you have the cash. The stock Mikuni BSR-36mm vacuum carb really stinks. That will be the biggest performance mod you can do at first, and that carb will be more susceptible to an athena 434 big bore kit, or even a 470 stroker if you decide to go that route one day.

I had a rev-max CDI on my Z for about a year before I cupped a valve, the rev max was bought in early 07, I rebuilt the entire head in the beginning of 08 with dual rate DRZe springs, kibblewhite valves, and a DRZe thinner base gasket which raises the compression from 11:1 to 12:1, and threw a dyna non-programmable on in June shortly before it was stolen in July. You can buy the entire DRZe kit from Paul at Advantage cycle, includes the springs, the base gasket, and DID HD3/4 timing chain. Really woke my bike up quite a bit, and it is a great reliability mod, makes the Z motor bullet proof.

I agree with Erik though, as long as your not bouncing off the limiter constantly or racing it you should be fine.


Just my $0.02

i will be using it for racing   at the drag strip and i probly  will be bouncing  off the rev limitor i am gonna push the motor   till it goes than i will rebuild it as a stroker motor with nos   ;D   but my nabior said instead of nos   we can do a turbo on  it. i should be getting my eddy carb really soon

stiffer valve springs will be needed then. edlebroc carbs stink though, very hard to set-up.

where do u find an  fcr carb?   i here about them  but i dont evan no who makes them

i put a edledroc carb on my 400ex never ran right (junk). ended up back with stock and bought a 450.

Just google fcr atv carb. But I know alot of people just buy stock yfz carbs because they come FCR.

Yeah to me it seems Edelbrock carbs are hit or miss, go with the FCR-39. Find someone who is parting out their YFZ-450 and snag it up. Take a while to dial it in but you will be impressed when you get it spot on.

k thanx for the help   is there anything that can be done to stock carb  for the time beeing?

If you pull the slide cover ( the top black cover held on my 2 screws) and take the long slide spring, and cut 1 coil off, don't cut anymore off, it will increase the throttle response a tad.