KX250 Chassis With 500 Motor

[BigGreenMachine]

More please! What did you use to cut them down with?

[don46]

The aluminum part of the swingarm isn't to critical, it can be off a little and not hurt anything. The spacer has to be square, I cut the swingarm on a mill and the spacers on a lathe. Like I say the swingarm isn't that critical, it could be cut with a hacksaw.

The attached pictures are for the head stay, the stock stay must be cut off and either a bracket such as I have or none at all. The bottom motor mount on the 250 chassis will fit, the front needs to be cut off and repositioned, and lastly the motor mount at the rear of the motor needs to be bored to 17mm

[BigGreenMachine]

Cool!

Step one - split cases and drill rear motor mount on drill press
Step two - after installing the motor install the bottom motor mount bolt
Step three - cut front mounts off, bolt them to motor and line up in new position, tack then weld
Step four - fab top mount for new head stay

Very straightforward IMO.

Thanks for the pics, appreciate them.

[gwcrim]

Man this is killing me.  I have an '02 250 as well as a 500.  Good thing I don't have a machine shop!  Or maybe it's a BAD thing.   

[gowen]

Man this is killing me.  I have an '02 250 as well as a 500.  Good thing I don't have a machine shop!  Or maybe it's a BAD thing.  

Crim, that is what killed me too.. But decided I wanted to keep my KX250 for track racing.. Now, I just use my YZ for the track only. I wouldn't dream on dropping a 500 into a track machine. I am much faster on a 250 on the track than a 500.. Just the power is easier to corner and jump with. But, trail riding? a 250 feels like walking.. Cool project though! I can't wait till work slows down and I can get out and just ride.. Can't even get that in these days.

[don46]

Cool!

Step one - split cases and drill rear motor mount on drill press
Step two - after installing the motor install the bottom motor mount bolt
Step three - cut front mounts off, bolt them to motor and line up in new position, tack then weld
Step four - fab top mount for new head stay

Very straightforward IMO.

Thanks for the pics, appreciate them.


I have fone three of these now, only 1 did I split the cases and drill the others it did while the motor was together, there are only 2 small areas that will have to be drilled maybe an inch on each side, the rest of it is hollow. I would cut the mount off the front before I tried to install the motor. Yea, I forgot about the pipe, that probably took the longest to get right, I used a KX 500 pipe and took the time to insure I didn't change any of the lengths. I have seen several with CR 500 pipes, most will say they work good, personally I've not tried one yet, I have one set up but haven't tried it yet. I looked at the Zip Ty pipe as well and thought it would be the easiest to modify. As far as taking the k5 on the track, I wouldb't be at all afraid to do it, it handles and feels like a 250. The 500 in my avatar is based on a 250f chassis, it handles like a dream, feels so light, but way to much fab work to get it right.

If you need any more pictures of something specific or questions, feel free to ask.

[gwcrim]

the stock stay must be cut off and either a bracket such as I have or none at all.

How safe do you think it would be to go w.out  the head stay?  The old time air cooled bikes didn't use them.

[BigGreenMachine]

If you chose to leave it then reinforce your other mounts for the extra strain!

[gwcrim]

Tell ya what.  The only thing that's really keeping me off this job is the pipe.  Everything else, I can deal with.

So what's the easiest way to handle the pipe?

[don46]

If I would have known about the Zip Ty pipe before I did mine, that's the route I would have gone. I looks like the CR pipe requires some work as well especially if you don't want to take the ball pein to it to get it to fit around the water outlet and the kickstarter. I think the Zip ty could be used easily

[gwcrim]

I'd still have to cut up the Zip Ty, right?

What about the head stay?  Think it would be OK to run w.out one?

[don46]

That is correct you would still have to cut the zip ty, but it doesn't look like it would be a big job. As far as the head stay, you could probably get by without it but you may ge more vibration, I just don't know. As far as the head stay, it could be made from steel rather than aluminum if your more comfortable with steel, not a big job to make. I did find a pipe in europe that was made for a 500 motor in a 250 chassis, it was a company in italy called Jolly Moto, but the price was $1400 US, that didn't work for me. SPES used to make a pipe, but now there all under the DOMA umbrella and they don't list one in the US, perhaps they do in Europe.

[gwcrim]

Take a look at the job this guy did on his hybrid.  That's one nice pipe!  Can anyone make out who may have made it?  There's a tag welded to it.

http://photos.everything2stroke.com/showgallery.php?cat=500&ppuser=8616

[BigGreenMachine]

Me thinks FloTek built that pipe. Guessing they had the bike to do so because it sure is a nice fit.

[gwcrim]

Well I wonder if they kept the specs?