i have this 1989 honda GB400TT cafe street bike and it has an RFVC 400 engine. currently my bike is not running due to the lack of compression and possible damage to its piston. i did some research and so far i only got info from www.oldrice.com that the GB500TT(which was sold there in the U.S during the early 90s) ha a downsized 1989 XR600 engine. and generally, the GB400 and 500 look exactly the same and share a lot of similarities. now is it possible to put an XR600 piston into my 400 and not worry about anything else?? those who have owned or still own a GB500 before please share your ideas. take a look at my "garage" if your wondering how a GB looks like. i labeled it as an XR400 though.