I've also got an 84 CM250, cool to see another cm, everytime i mention it people think i have a speech impediment or something and assume I'm saying CB.... uh no its a CM pretty similar but its not a CB haha
I've had mine for about 3 years, but have never found a good site with info on them.
Mine is belt driven, but you should have a good bike, It's the most reliable bike I've had. I'm about to sell it for something else, and i know i will most likely never have a bike as reliable as the cm250