DO NOT PUT A PENNY INTO THAT BIKE MONKEYWRENCH!!!
All of the motor in the world will never make up for geometry and suspension.
That said all of the motors now are vastly superior to yours.
Find any 250 2t that is made in this millennium, the newer the better and start there.
I have a 05 YZ because I really think that they are the most versatile-more on that next paragraph-
and are a ultra reliable motor and parts supply. That said I love the RM too. I also would buy the
KTM and have a KX 85 made into a 105 that just plain scary.
The Honda is last on my list and still would buy one.
I had a really good running 01 that was as fast as my 265.
My 265 has a Kustom Kraft kit then reported. Do not for a second
think this is a cross bike; it is set up for woods. I also have a WR 1st and 5th
gear, 2,3,and 4 are YZ. A WR 450 rear spring is the hot ticket as well for my weight,
this is a much lighter bike then the WR and firms up the rear nicely. I have the forks being re valved
and the rear is being swapped out for a 18 inch with a trials tire as I type.
I think of this as a Yamaha version of a KTM 300. I also feel it is a much
better bike then the 300. That said I don't see any modern 2t 250 that is bad,
just each has it own personality. Yamaha's can be altered much more then the
others. Trail bike, add a Flywheel weight if you choose.
I went out about 8 weeks ago in a downpour of sleet ,snow, and standing water everywhere.
I watched to CRF 450 struggle all day and flame out, I was able to pick all sections with great ease.
I did stall once. I have ridden my bike and then a YZ 450 back to back and there is
no way in hell that it out pulled me. I love the 265 motor, but I like the frame and suspension better!
I read that a modern 2t is good for 0.2 HP per cc, the modern 4t 0.12 per cc.
Grab a calculator, the bikes weight, the projected rounded HP and have at it.
When I crunched all the numbers, Yamaha had the answer.