I can't identify my bike... Serial number ACM05F006119 20 inch bmx?

Serial number is quite useless, but still, a bike with a similar serial number can be seen here: https://bikeindex.org/bikes/633505

Serial number may be similar by chance, or it may come from the same factory.

If your bike is similar to the bike depicted there, you may have got a bmx branded MCS, unlikely it is from 80s, likely to be some mass produced aluminium thing similar to a bicycle. The bike in the picture above is from 2005. Check this models gallery: https://bmxmuseum.com/bikes/mcs/ to see if yours is similar to any of them.