They're great machines. The whole CB/CM line, 400/450... From 1978 thru about 1984 and the same motor used in '86 & '87's Rebel 450.
They came with engine counterbalancers, so they're much smoother than our vintage Honda twins. I've never heard of any particular weaknesses in them. They had 3-valve heads, two small intakes and 1 larger 'normal' exhaust.
They came in a bunch of flavors, primarily in external style, but some significant mechanical differences as well. CM4xxE version was Economy, with drum brakes and spoke wheels. CB/T 'Hawk' was the 'sporty' version with mags, disk brake up front and even 6-speeds. CM/A with automatic transmission. CM/C for the Custom (cruiser) version with extra chrome, mags, stepped seat, etc. The CB/SC Nighthawk which was a slightly restyled cruiser version. And finally, the motor used in the totally uniquely styled (for Honda at the time) Honda Rebel 450.
All great bikes for what they were - primarily inexpensive lightweights.
Your individual bike's condition will vary...