KX Guru Racing

CR500 Honda with CR250 ignition system.
What years will work and what will be the effect?
One of my buddies asked me these questions.
So, let the research begin!
Anybody have a idea?

I found this info at:
http://www.extreme2strokes.com/showthread.php?tid=1435

CR500 with 250 ignition...
Some of you might know this mod.....

Some guys in the US has done it, some even locally... Some guys love the swap some hate them....

Let me start by saying that the 250 flywheel/stator/cdi fits straight on, at least my 2001 CR250's did.... I went for the 2000/2001 setup because its digital....

The 250 flywheel are MUCH lighter and MUCH smaller in diameter..... They ignition curve allows the bike to rev higher, some guys has lots of mixed feelings about this swap, some say they start harder because of less flywheel weight, some say less bottom end, some say they are HARDER to stall.....

Here is what I have done.... I pulled my jug to rebore to next oversize and thought that the porting does not match the 250 ignition at all.... So I went ahead and ported the bike a little different, more exh duration and reshaped transfers.... I also reshaped the head, its about 2cc smaller, different squish angle, width etc... VCR is still very low @ 12:1 and cranking PSI is 125....

The pipe is about the only thing holding it back for a top end 500 motor.... I think the CPI pipe will shine with this setup, much say they are total junk, but IMHO its because the porting don't match the pipe....

Ok, so I took the bike for a ride after assembling it with the 500 ignition combo... The bike ran strong, but the ignition kept it from revving and I think this type of port job is a waste for a 500 ignition.... I had the idle issue, so this made me to swap the ignition with the CR250 ignition ( i thought my stater was messing with me)

Let me start by saying the bike is still waaaay rich at 182 main jet.... SO i modded the 250 stater plate to fit....

First impressions:

They bike starter def easier or at least the same (advantage of digital I think) even with the lighter flywheel....

The bike idling issue is sorted (maybe its just my stater, but not sure)

I warmed the bike and took of, I immediately felt the responsiveness of the lighter flywheel, there is NO comparison let me tell you.... Flipping the bike around is also def easier.... The biggest surprise was, MUCH less vibration??? What the heck???

Ok, so after a slow riding of fiddling the throttle and warming her up it was time to kick up some dirt.... WHAAAAAAAAAAAAAAT THE HEEEEEEEEEEEEEEEEEEEEEEEEEECK!!!!!!!!!!!!!!!

This bike revs like a 250!!!! The port job even make it rev to the moon and the bike runs like a freaken rocket.... I think the combination is awesome... This 500 revs and make power up there.... A stock 500 don't rev, trust me.... This bike is not for beginners.... Its scary and its still bogging when I twist the throttle, but when it clean out, it is scary fast and just leave ditches in the ground... I think the 250 setup is awesome, I think a top end port job with it, is even more awesome!!! I can tell you that if you want the best of the 250 setup get the bike ported to shift the power to upper rpm.... The bike did not loose any low end grunt that I could feel, but I think this is also to a little higher transfer duration and the diff head design....

I had no idea that a 65hp+ 500 MX bike can rev like this... I also think the pipe is holding it back.... I don't think the big motor will like the very high rpms to much, but this is a tough motor and the fun factor vs a shorter life motor (who knows?)

By FAR the hottest running MX bike I have ever ridden... Maybe taking it to the dyno, want to check the A/F

Service Honda makes a kit...

http://twostrokemotocross.com/2012/09/s ... on-system/

1984-2013 CR500R/500AF Hi Power Digital Ignition System & Light Coil

A limited number will be available, pre-order now by emailing jeff@servicehonda.com

The Service Honda digital ignition represents a huge leap forward for the CR500 engine. This ignition completely transforms the bike. The transformation is appearent as soon as you start the bike, turn the choke off and let the bike idle while you put your gear on… and the bike will not stall, and that is just the beginning of the improvements. Once your gear is on and you are riding the bike the next thing you notice is the improved throttle response and big increase in low end power. Throttle response on long technical down hills remains consistent through out the decent with the new system, a quick twist of the throttle produces instant power to easily clear an obstacle. The digital system uses 26 maps with a new map every 300 rpm compared to the old analog system that used only a few. The vast increase in the number of maps results in much smoother power delivery. The smooth power really improves traction vastly, even on a hard slick surface resulting in faster times and less rider fatigue. The power is so much smoother you can be fooled into thinking the new system makes less power, this is not the case the digital system actually makes a bit more power than the old analog system.

The "KX riders" for CR can be found here,
http://www.cr500riders.com/
and http://www.bannedcr500riders.com/board/index.php

Thanks Tuck.
I did a lot of looking at Banned.
I'll be hitting the other up tonight.
Looks like it can be done but there is only seat of the pants reports so far.
It would be nice to see some dyno specs but it seems that I'm asking for too much