Originally Posted by BikePilot from DisTech's DR350 build thread
IIRC the primary drive ratio (crank to clutch basket basically) is different between the 350 and 250. I know that for a given final drive ratio my '94 250SE turns more rpm than my '96 350SE. Also note that your 250 motor is a 250SE. The plain S was kick start only.
primary drive ratios:
DR350 20:64 (3.200)
DR250 22:62 (2.818)
I'm led to believe that the lower ratio (from the 250) will be easier on the tranny and harder on the final drive. I'd rather be replacing chains/sprockets than trannies, so I'm going with the 250's primary.