I have a 2001 WR426F that has been in supermoto trim since the day I bought it new in late 2000, it has been a wonderful machine. 3 years ago I did a 444 big bore kit to it, had the head cleaned up and ported slightly and it was a definite improvement. Like all of the after market pistons this Weisco started to rattle around in the bore after a few thousand miles, and I am sure the rod is a little long in the tooth. Long story short, I was debating rebuilding this WR motor from the ground up when I came across a brand new YZ426 motor in a crate complete with carb, so I bought it, but now I am having second thoughts. My question(s), How much different is the YZ gearing than the WR (same year engine)? Were there any other differences in the 2 engines besides cam timing and throttle stop? I will need to keep the lighting coil because my bike is street legal so I have lights and signals, do I just swap the lighting coil from the WR motor over to the YZ motor? is there anything else I need to do electrically to do that right? Also I read allot about counter balancer woodruff keys back in the day, I can say however that my WR motor never had an issue with that, so is there a hardened (harder than stock) woodruff key that I should consider replacing before I put the motor in the bike? I guess my main fear is that with the YZ gearing I may not like it as much on the street, so I need some input on that from those of you with experience. I have not committed to anything yet other than the fact that I have a brand new YZ engine in a crate with Japanese writing all over it sitting in my garage, I will not be putting the big bore kit on either of these 2 engines this time around as I really don't think the reliability is there with after market pistons and the extra bottom end that I got out of it was really not worth the piston slap noises I had to put up with after about 6 months of weekend riding. So the bottom line is this, if you had the choices I have now of (1) installing a brand new engine including swapping the ported head from the old engine, swapping the lighting coil from the old engine and calling it a day or (2) rebuilding the old engine which I am sure will require all new lower end bearings, a few gears, shift forks, clutch basket and clutch, crank work most likely (Falicon), with a knife edge rod etc. I am certain I can sell this crated engine to a kart guy on ebay and not lose a dime, I paid $1400.00 for it. I guess the other thing I could do is sell the old engine on ebay for close to a grand and end up paying $400.00 for a brand new engine which would not be all that bad. Thoughts? suggestions? Thanks.