That rules out pretty much anything Pre '92, to be on the safe side you'd want to have Euro 4 compliance which would be from 2005 BUT was only mandatory from 2007.
I like the way that the london transport site says the way round this is to 'upgrade' to a second hand post 2007 bike.
If you live inside the Nth Sth circulars then you can get a 100% discount for 2 years to give you time to 'upgrade' before you're hit with the daily charge.
You'd have to be tempted to 'upgrade' to a pre-79 2 stroke and get the historic vehicle exemption and be able to wave smoggy a finger
They are using the over 40 years old category so pre-79 is the magic year