About a year ago I picked up a great looking 1998 Kawsucki KX500. After riding the bike several times, horrible mechanical repair choices which occurred prior to my ownership of the bike combined with my foolishness of not more thoroughly inspecting the engine led to a pile of engine parts cluttering my shop & a nice rolling chassis melting into the grass out back. At first I was thinking to make the motor right & reinstall it. Then I got to thinking just dump the motor or keep it as spare parts and buy another running 1992 or newer KX500 and start over again. Still haven't really come to a final decision on what to do with the mess.
Fast forward several weeks...
Just last week on whim I picked up a basket case 1981 CR250r in overall good condition except for disassembled motor with a bad crank. This particular CR was the last Elsinore & the first cr250 w/ liquid cooled engine & mono shock. It was know for being top heavy with clunky radiators & performance was ridonkeylous. I looked into getting the bike running & rolling anyway. What I found was whether I repair w/ used parts or swap in a good motor its about the same price. Sitting there staring at a screen full of fleabay cr250 parts I got to thinking if the price is all the same on fixing or swapping an engine why not just swap in something a notch up on the 250 engine. What I found after some research & some forum thread conversations was that I could stuff an early '80s air cooled cr450 or c480 straight into the 250 chassis as well as vice versa. So I know I am thinking to dump the 250 engine for what its worth while keeping the cr250 rolling chassis with any and all components compatible with the installation of a cr480 engine. When I find a cr480 engine on the cheap, I am gonna pick it up, slap it in the 250 chassis thus achieving a more powerful motor with lower center of gravity & possibly less wet weight due to the loss of liquid cooling.
Now back to the KX500 project...
So now I am all hooted up & getting excited at the prospect of building an old school air cooled big bore two stroke ass whooping dirt bike. Thing of it is I still got the pile of parts KX500 to deal with and I need to dump the old cr250 engine before I can move forward on a cr480 build. That means the cr is going on the back burner for now. I am thinking its time to make a decision on what to do with the KX500 though. Obviously I need to either rebuild or replace the motor. I was thinking at first if I was gonna swap engines it was gonna be a 92-04 engine same as the one the KX500 already has. After this whole early '80s Honda project sidetrack though I am off on a tangent though. I am wondering if there are any air cooled big bore two stroke Kawaski motors that would bolt in or could be made to bolt in to the 1998 KX500 chassis fairly easily.
Any info anyone has on engine swapping between 1984 and earlier kx400 kx420 & kx500 air cooled engines into 1985 and newer liquid cooled chassis please share.
How close are the engine cases between 1984 air cooled engines & 1985-87 or 1988-04 engine cases?
Engine heights for the old air cooled engines?
What other old skool air cooled 200cc or larger KX or KDX engines might fit?
