Ughhh.
These debates always come up. Here's my view on things.
The 400ex is a great handling, nimble, timid trail quad. The reason people build them up is because of their chassis. Like I said, in stock form, the engine is very timid and mellow. That being said, you can turn them into monster's.
A WELL-BUILT 440 or 460 stroker can really run. But, I view it as, if your goal is to build a high-powered race quad, and piped and jetted 450 of any brand is the equivelance of a built 400ex. So, if you plan on racing, I would still stay the 450 route. Most pro's race bikes are pushing 60-65hp. Im sorry, but you're not going to get that out of a 400ex without nitrous.
I view the 400ex as a fun, nimble weekend warrior trail quad. While, being a great amatuer MX quad. You can get them to handle really good, but not go quite as fast, unless your comparing them to a piped 450.
Right now, I am plenty satisfied. I own two of my favorite quads The only think I would ditch the 400ex for is a raptor 700, but it's not like something Im desperate to do.
1989 Yamaha YFZ350 Banshee
DMC 916 Exhaust__K&N Filter__Boysen Reeds__13 Sprocket__+2+1 Lonestar J-arms__Works AT-Steelers Triple Rate Shocks__White Brothers Rims__Renthal Banshee Bend Bars__Powermadd Handguards__UFO Plastics__Nstyle Graphics__Ceet Cover__Turner Bumper
"It ain't fast without mixed gas"