Maintenance & Technical > KX500 Steel Frame Conversion (SFC)

Need some advice on conversion

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vwcamper74:
Hi everyone,
I am currently toying with the idea of putting my 500 motor in a newer frame.  I have read all of the past posts regarding conversions but still don't know which the best option will be.
What is the handling like when you put the 500 motor in a 04 or new chassis.  I will be mostly doing high speed desert riding and I want something that is stable at high speeds.  Reading up on the kx250 frames has me a bit confused as the 04 kx 250 had a 27degree rake and the 05 and later went to 26 degrees.  Are the 250 frames good for high speed and would the reduction in rake in 05 reduce stability.  The trail on these frames are less than on my 500 but I honestly don't know how trail affects handling.

Would a 250f frame offer better handling than a kx250 frame and thus be a better conversion?

Lastly, assuming I picked one of the above options to do a conversion, how would the handling compare to a 500af conversion-again high speed stabilitly is important to me?

Sorry about all the questions but if i'm going to go down this route, I want to make sure that I start with the right chassis.

Thanks - Mark

kxpegger:
I have an "08" KX500AF from Service Honda. I ride Nevada Desert (high speed). The front does get a little squirrley from time to time but I haven't really played with the suspension settings or adjusted the sag yet for my weight. It's not so bad that I'm worried about it or that it slows me down but it is noticeable compared to my other bikes. It's not enough for me to even consider a steering stabilizer either. I may put just a little more preload on the steering bearing nut and that should probably take care of it.

vwcamper74:
Thanks kxpegger,
What kind of speeds are you doing when it starts to get squirrely and is it doing it on rough ground or at a certain speed.
Probably a hard one for you to answer unless you have ridden a kx250/500 conversion but do you think the handling would be similar to your AF with a kx250/500 conversion?  The reason I ask is that I can get a 250 chassis a lot cheaper than a 450 chassis and I would be able to do most of the conversion myself.

kxpegger:
It handles the big stuff fine. Usually when I start to notice is 4th and 5th gear. Smaller repeated high frequency hard pack (concrete) bumps mostly when on the gas. I can't really blame the bike as I'm still tuning the suspension. It's getting better everytime I go out. Most of my adjustments have been to turn the rebound down front and rear. I've left the compression alone for now and will try different tire pressures when I think I'm getting close. With the stock front D742 tire it had a tendency to really push the front end in the deep tight sand wash turns. I put a D745 on front and it made a world of difference. After I think I've got the suspension dialed in I'm going to play with the fork height and find the best setting for turning and stability at high and low speed. I'll figure it all out someday. Took me 6 months to get my RMZ450 dialed in for best overall offroad performance for the type of riding I do.

What I can say for sure is the AF is head and shoulders above the KX500 steel frame handling. One of my riding buddies has a 97 KX500 and we traded bikes for about a 1/2 hour. He was amazed at the difference and didn't want to give my bike back.

Don't know what to say about the 250 conversion. Do you mean AF or steel? Service Honda is now using the 250F chassis unless you ask for the 450F. Either way I have no experience with the 250 conversions.

Hope this helps!

The Flyin Hawaiian:
Im building a 04 KX250/500. Its been pretty easy to do so far. Im at a stand still right now because I need to save some money up for the exhaust. I have alot of time on 03, 04, and more recently the 07 KX250s. The 04 that I am using was bought new by me and raced in enduros. Its a very stable chassis and turns well also. I raced a 02 YZ250 before switching back to KXs and the KX is as stable as the YZ and turns better. I dont think you would be disappointed in using a 03/04 style chassis. The 05-07 chassis is changed quite abit. At first glance it looks identical to the 03/04s. Upon closer inspection, you start to see the changes. Ride them back to back and you will immediately feel the difference. The 07 feels 125ish, very nimble and narrower at the footpegs. A problem that yu will have with the conversion is that an IMS or Clarke will not fit, not even close! I will be using the stock tank for now until I can possibly have a carbon fiber or aluminum tank made for it. It will be pretty spendy though. The stock tank fits perfect! 

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