1979 cb125. Thoughts? Warnings?

[redbirds_imp]

Had an SL 100 with that same motor in the early '70s. Between my brother and I we thrashed it unmercifully trail riding but were unable to break it. Later we converted it to a 100cc motocross bike by adding a cam, re-jetted carb and an open exhaust can. My brother raced it for two years and still the motor survived although the frame and wheels not so much.
I would love to find one in that condition.