Most performance parts dealers recommend installing a keihin fcr 39mm carb on the 400ex to improve performance, but the price is pretty steep. I did some searching and found that the fcr 39mm (horizontal) carb was designed for road racing and comes stock on many street bikes, in particular, the suzuki gsxr 1100 '86-97 and gsxr 750 '86-95. I was wondering if it would be possible to get an fcr carb from an demolished gsxr and use it on a 400ex? The only problem I can think of with this idea is the fit of the fcr to the air boot and the intake of the 400ex, but the carburetor spacers on the fcr can be removed and changed. Does anyone have any information or ideas that can help me figure out if this is possible?