Not quite a KDX but close enough.

[zz3gmc]

I havent been on here in a while but heres a hybrid that I finished in May 2011 and have been riding the wheels off of it since. Hopefully Ill build a KX/KDX project someday. Some may recognise it from other sites.
04 KX250/500

[rbates9]

Nice. Do you have the details of the build?

[Julien D]

Wow, it's a monster! Very nice work. Would love to see the details.

[zz3gmc]

The build is pretty much the same as the KDX200 hybrids. Maybe easier in some respects. The engine cases need to be opened up like the 200, 17mm. The engine will then bolt into the existing lower motor mount, The front mount has to be moved to fit. I used a 500 airboot with a adaptor plate. The airbox is not modified. I used a intake manifold from a 91-94 KDX250, this angles the carb away from the shock and the KDX shares the same reed cage as the 500. The headstay mount on the head needs to be shortened and redrilled. The frame headstay mount needs to be cut off and centered with the head/headstay. Fab up some upper mounts. I used a Service Honda KX500 AF FMF Gnarly/Q silencer combo. Except for some slight clearancing, denting, there are no mods to the pipe. This is so I can replace it easily w/o major fab work. The large capacity Clarke tank is off of a 05-07 KX250. The 03-04 big tank wont fit. Niether will the 03-06 KX125 tank, same as the 03-04 250. No way, no how! The 05 KX250 got a new engine from the cases up. It is very similar to a 99 up YZ 250 in configuration. In other words, the cylinder is more straight up and down than the 04 and below KX250s. This means that there is clearance for the cylinder. Which works out well with the 500 since the cylinder is much bigger. Very slight heating of the tank was needed to clear the spark plug. The tank can be put back on my 07 KX250 w/o any issues. It has a Moose lighting coil so the lights work decently. Suspension is revalved by WER, its what was on the 250 which was my old race bike.
I traded my old DR350/435 dualsport to my brother inlaw for the 500 even up. The 500 had a mild seizure but only needed a slight clean up of the cylinder. The bottom end was rebuilt by me with new cases, crank, bearings, clutch basket etc. The only thing original was the trans. I rebuilt it for him a year before I got it and he hardly rode it before he siezed it running some questionable old stale fuel. After parting out the 500 chassis, I have around $500 into the whole build. I have a large supply of KX parts here also which helped keep the cost down. My wife loves it and wants me to build her one now!