85-86 engine is totally different to the 87 and up. 85-86 is case reed induction
(cylinder needs to come off to change reed pedals).No power valve system.
87 up is piston reed induction and has the powervalve exhaust system. Nothing really interchangeable
between the two engines at all.
Stock bore for 85-86 is 249cc and the 87 up is 246cc
85-86 are 5 speed 87 up are 6 speed
The engine cases are blue on the 87 and up, as opposed to the satin finish on the 85-86
85-86 has sigle pole frame support infront of the engine, 87 up has Y type pole frame support.
85-86 weekest frames (always check for cracks around shock mount areas and frame mounts).
True 85 had only straight seat and black nose peice, 86 was also straight seat with option for t seat and had blue nose
cover. 87 up blue nose t seats.
87 had larger intake than 88 up with totaly differnt bolt pattern for reed cage.
Suzuki was always up against the wall every year trying to compete with honda's 250r so they made major changes from 85 to 88
from 88 on up not so drastic of changes but changes non the less..