kx500af vs kx500sf

[hybridjunkie]

Which of these two are better

[Ims Roll]

Personally i do not own a sf or af conversion but i do know that steel frames flex better then alm frames... i like the flex of a steel frame as i am a big guy and i ride desert but if you are a track guy i would assume alm would be better, it's all up to you and what kind of riding you like.

[motopunk]

in case of damages is a steal frame easier to weld. you can weld it directly beside the race-track and ride again on same day.. 

alu frames need a good heat coating procedure before welding and after that, you have to wait 3 days or more, to get riding hard again with it..

for mx is not essentual which kind of frame you use.
 these conversions are shoulded in better ergonomics of the new age bikes vs the stock k5-frame with the big tank on it which is all designed in the late ´80s and never changed. the actual bikes are nearly all manufactured with alu frames.

 and the kx- motor is still the strongest 500cc  ever, that was produced in stock..   

[don46]

you have to be more specific on which steel frame. I've had several that were in the 99-02 chassis, they were better than the 500 chassis. I currently have a 05 250f chassis conversion that I've had about 4-5 years, I had also built a AL framed bike a couple of years back thinking we were going to switch to the al framed bike, long story short my son like the steel framed bike better so I sold the AL framed bike. Fast forward to 2012, last winter I built another AL framed bike to use for testing motors, this one I did equip with Showa suspension so as we move forward we will test chassis as well and in the end 1 will leave and I'll keep 1. I don't think you can go wrong with either frame but, the steely is easier to build so that could be a deciding factor.

[motopunk]

i personally like the ergonomics of the j and k frames . and yes youre right the steely conversion was very easy to made against alu-frames , where you have to cut and replace the rails for the 2 stroke engine.in the end its the riders attitude on which frame he feels better on the track. 

i also like the look of the newer alu-framed bikes conversions. but anybody has to know that welding aluminium isnt easy as welding steel.
 and you dont need the newest bike to be fast on the track and have lots of fun.  you need a bike that works like a good marriage to the rider... 

[hybridjunkie]

I was thinking about using the 04-05 2 smoke chassis of the kx 250 but would love to know if the 07 would work too

[don46]

I was thinking about using the 04-05 2 smoke chassis of the kx 250 but would love to know if the 07 would work too

the 07 is not different from the 05 chassis or at least anything significant, I think the 04 to the 07 were basically the same chassis, for sure 05, 06 and 07 were the same.

[hybridjunkie]

Would the 500 motor work with the 07 chassis as well as the 04 will ...the 05-07 aren't common

[don46]

one thing for sure, old two strokes keep on running, you can find four strokes all day long but not so with the 2t. If you can find any of them it would be a score, from 03 on the head stay was at the rear of the cylinder so that would be a big help. was it me I would go for the 05-06 chassis if I could find it. Should be a pretty easy conversion, building new motor mounts and maybe not even the bottom ones just the front and a new bracket for the head stay. as with all of the conversions the pipe is the biggest pain, I've take a couple of the stock pipes cut and twisted to get them to fit. The one service honda pipe I got looked like somebody at SH to a hammer to it, seriously.

[hybridjunkie]

Would you u happen to know what year of the kx500 was best?

[don46]

assuming your talking motor, pretty much from 89-04 would be good. some folks will say the 89-90 motors were better and progressively got worse, they would say the tooling started wearing out from the inception and progressively got worse, for me any of those years are fine. older 500's are getting harder to get parts, the KIPS valves have been discontinued, as I recall the 86-87 motors had a different spline on the clutch and I'm sure there are other parts.