I'm about to pull the pin on a YZ450FX.
How much better is it than your "custom" WR450 and the Beta ?
The full-blown 2008 WR-to-YZ feels like a dinosaur compared to the FX.
It runs much better, less engine racket, better suspension, and much, much better build quality than any other Yamaha I have ever owned.
In everyway, the FX is better, accept two: the ergos are more compact, and the off idle torque is less.
Both can be fixed.
Are there conditions, like tight woods where the Beta is better than the FX ?
The BETA is better on the very tightest, steepest terrain......but it has a much more 'reserved' power delivery, even with a pipe and remap.
The BETA turns much tighter. The FX needs to have it's steering stops modified to be truley woods worthy (which I will do).
The BETA is very, very civlilized to ride. Smooth, compliant, flat power.
The Yamaha is more fun, but it tires you out when you use all that 'fun', and it's much less compliant in the ride. I don't mean the suspension, I mean the overall flex of the bike.
The Yamaha has more power everywhere, and the suspension is world class. You can cross ruts at speed and it's no big deal. On the BETA or on a KTM you had better hold on tight...
Is there anything about the FX that is turning you off ? Is the off idle stalling curable ?
It doesn't have an off idle stalling problem.
It has the same problem just about any modern FI bike has, and that is the power is kind of delivered in a 'crude' state. You have to fine tune it.
The Yamaha intake honk is annoying, as is the limited gas tank options.
There is an IMS 2.5gal tank coming that requires no modifications.
The intake honk can be lessended with some Dynamat and some earplugs.