Yes it will but it's not a direct bolt it. Some slight modifications will be necessary. Also may have to custom cut the drive chain. Take your time check and recheck all work, do it right the first time.
No
Nope
If there the same year it should fit.
Unfortunately, a newer yz250 model engine will not be able to fit the frame of a 1991 model. These engines were designed to specifically fit the frames of certain models of the vehicle and are not universal.
no a 250r motor will not fit in a 200x frame but it will fit in a 250r frame
The 125 forks should fit the 250 as long as they are both the same frame style and close years.
no.
Yes, but you will need do some fabrication to the frame in order to fit it in correctly.
Size wise, it would fit, however it wont bolt into the frame if that is what you are asking.
no
Yes it should fit the frame not sure if tank will fit as the 91 barrel and head are bigger
Should fit it's the same generation motor.