Will a 400EX top end bolt on to a 350X bottom end without mods? I know that the heads are a litlle different, but the cases appear to be the same. Also, are the engine mount locations for a 400EX in the same places as on the 350X? My freind bought an 85 350X that was run without oil, and it has a chewed up head. We were just brainstorming the other day about whether or not a 400EX would fit right in. It sure would be sweet to have an electric start 400cc three wheeler to shred the dunes on.

 

Take some external measurements and compare it to a 400ex, all i can tell you is that a head pipe from a 400 ex will bolt to a 350x head it just wont mount into the muffler, so its possible that it will work. You should probably go with the 400ex piston as well