I had heard those XR engines were tall. At one time I thought about trying to build my own TRX 700xx using a 450er chassis and a XR650L engine (love the 450r chassis and wanted the power of the 700 without the IRS, lol), but found out I would have to modify the frame extensively due to the height of the engine. I did hear that a 400ex chassis might work though . . .
Jason
85 ATC 250R - restored stock other than 18" rears, nerf bars, Honda key switch, 14T front sprocket, and white tank and plastics (except rad shrouds)
87 ATC 200X - restored stock other than 18" rears and nerf bars
84 TRX 200 - rough but complete budget restore for wife and eventually daughters to bum around on
Eton Viper 50cc - oldest daughter's current ride