KDXRIDER.NET

I am a hopeless analytical tinkerer, cant stop my self
I have read just about every thread related to KDX. It is hard to find info on bike running 100% Fredette mods ether they don't talk about and they just ride or ?.
my bike is running a KDX 220 USCHROME plated cylinder that was ported a head that was milled and carb that has been bored to 36 all the work was done by Fredette's shop for some one else I purchased the bike with just the break in done.
standard aftermarket reeds nothing fancy FMF torque pipe or woods pipe with a turbine core 2 silencer, I notice fredette does not recommend the woods but does recommend the REV version for the 220.
I have what I have, jetting was real fat from the shop 45 pilot 1173-3 needle 160 main. I ride year round so even in the summer when its 90-100 degrees.

I am consistently riding with 250's and 450's of all colors and am trying to get an edge this all is after coming off a 650 four stroke to the KDX.
what I am after is as close to all the power and the smoothest of power bands.
what I found with my bike is jetting the bike a little lean or right were it is suppose to be the power band flattens out between 3/4 and wot.
for some reason related to the first sentence of this post I tore my silencer apart cleaned it cut about 3 inches off the end repacked it and rebuilt it. there is no noticeable noise increase but there is a power increase. the effect was a snappy leaner running condition that caused the powerband to flatten out between 1/2 throttle and 3/4 throttle. current jetting at that time was 42 pilot-needle- CMG-3 main-158-airscrew 3/4-1. out. changed the needle position to -4 and airscrew 3/4-1 1/2 out.
the result is a smooth fast response that revs to the moon. find my self riding in third all lot seems no mater what gear I am in it just pulls.
this is running 13:49 drive and I change my fuel ratio to temp and humidity from 50:1 to 40:1 as the fall and winter comes on I will have to adjust and find the right D needle for that. with the temps over 80 and humidity around 50% the D needles are to rich, when temps get below 70 and the air dries out then I will be trying the D needles again.

as for sss there is only one sweat spot for this set up then it pulls from down low to up high. a alot better than the KX 250 with a fly wheel weight piped for the woods or more controlable or maybe the control part was the suspension. I hate it when I break my own rules,(dont ride some one elses bike) fast is all relative to condition so untill I get the KX forks on, fast is as fast as my suspension lets me go after breaking the damper rod well thats about it.

If you get your slow speed circuit and high speed circuit dialed in to your elevation and riding conditions the rest of the fine tuning can be taken care of by the needle, position of the clip on the needle and airscrew.
the main investment is time wich most don't want to take.

all of this has been covered by this forum THANKS guys!

In the KDX ONLINE MANUAL coming out next week, there is a section written by Jeff Fredette about performance and the KDX. This should provide some insight as to what Jeff has found that increases performance.

That said... most think about reliability and longevity vs. The highest performance available. Jeff doesn't have to worry about this but he doesn't get too crazy on modifications either.

Most of us folks like doing mods ourselves and only send out machining. The carb modifications are the most effective performance mod I think. A stock carb works fairly well... but a plated RB carb works much better. Just boring a 33mm carb to 36 as Jeff Fredette does, makes a huge difference on a 220... but does nothing on a 200.

On the otherhand, the carb mod that Ron Black does makes a huge difference on all models.

I like Jeff and he is a down to earth guy but from what I have seen, porting doesn't really help KDX performance all that much and can actually hurt it. You can take a dremel and clean up the casting marks yourself to help increase flow... but NEVER polish. The rough surface help the turbulance which help mix the fuel.

Probably not what you were after.... but there it is.

so the only difference between the Fredette mods and RB is the carb and the way the head is done? and knowing about the carb what is the difference in the way they do the head?

Probably just technique and or math... There are pics of RB's head mods on the site.... but I have never seen a Fredette head pic....

*EDIT*

Does Fredette cut a new anti-detonation ring? Alter the Squish band? Or does he just mill it down?

This might be what separates and engine builder of 30+ years from a Racing Icon.

Yeah, there's a lot to that! Porting is like a cam swap in a 4-stroke...It can change where and how much power is made in a certain area....There is always a trade-off....A port job for a works MX racer is going to make nearly no bottom-mid, but will hit like a freight train and show huge net increases on the top. Only problem is once material has been cut away you can't put it back. Just shedding some light on that. Whenever I read 'ported' the first thing that comes into my mind is "ported for what type of result?" Some factory race teams even had different cyls/motors for different track conditions! Must be nice!

thats the question I dont have the answer to is ported for what and how.

You could call Fredette...Most engine builders will log the cyl#, and keep records as to what was done to it.