It's currently built to take the 250cc - 400cc, the reason for this is due to the whole engine / cvt act as the swing arm and point accordingly where as the 650cc has a separate swing, but the chassis is very clever in that it could easily be adapted to take a larger engine it would just need a little work to configure it to add supports / pivot points for the swing arm the only down side is that it will lengthen the trike wheelbase,,,
The best option would be to prep the 400cc during the build and have the top end upgraded ie bore out and oversize piston etc,, common practise with many bikers over here!!!
It's set up to take 98 - 03 AN models really with standard carb, it will take later models around 05 but these have fuel injection so we can't easily reposition the carb but like Kevin is doing this will just sit through the rear bulkhead and then be boxed in, so the options are endless
I will be building the "R" kit using a 2008 400 donor. Some of the things I see that are different from the earlier models will require some modification to mounts. Here is a list that I have put together so far....
Engine head has spark plug installed between the valves dead center of the head, so clearance between the head and back panel may need a work around. The fuel tank is a different configuration and shape, again, the mount will require modification. The radiator is quite small and has a low profile cooling fan. This is a plus, and I intend to use the space as wisely as possible. The rear brake caliper is mounted on the right side of the wheel mount and not inside the wheel, this necessitates rerouting the parking brake cable and hydraulic lines, and possibly the ratchetting mechanism for the parking brake. The throttle body is Configured so it follows the same direction as the engine cylinder head. It "DOES NOT" point out to the right side as the carbs do. This may interfere with the fuel tank mounting but it is to be seen. There may be sufficient room to keep the OEM air box and sensors. The mono shock appears to be the same length, but the linkage connecting it to the engine does not have the offset on the privet mount. My cure will be to use a $20.00 2003 pivot rather than move the shock location to the centerline of the chassis.
Finally, the gauge cluster is MUCH LARGER and includes a tachometer, fuel gauge and temperature gauge. It also includes an air temperature read out as well as a "fault code" center to troubleshoot the ICU, fuel systems, and emission control system.
With the obvious advantages of a newer engine and the performance of throttle body injection, the use of the later model donor Burgman 400's to do a build represents a unique challenge.... To get it all to fit (neatly) in the Eco-Exo chassis. I will have my kit this summer and will be actively adding to this forum.