Here in Us we have some movements to such classes. In our local club in Texas, TVRC we have been running a decade class for..well, about a decade. While it seemed like a good idea back then, realize that now a 98YZF400 is a decade bike-and who of us could really tell a YZF450 from a 426,400?....As far as pre-90-it may be fun to have some of these bikes included regionally at meets, but there is a consequence. To me, only the last 500cc bikes from this era matter(JMO).-and if you look at what is happening now, with SVRG, AVDRA split from AHRMA-and TVRC now running modern support( guess who is a big TVRC sponsor-initials are V.I.)-with the decade bikes, just scored separately...well, I am going to miss some TVRC races. Hell, there wasa "practice day" at the local mx night track I used to race on( home of 12+ fatal accidents since 96)-and this track is not that ridable on even an 83-84 bike. Well, everyone was riding their modern bikes.
Hell, is this vintage? This is about old bikes, not old people. We now have some 20s -40s yr olds starting vintage racing-mainly on the 80-81 bikes(EVO?)-but then they go on to build vintage(pre-75) , and historic(pre-78) bikes as well. The era of disc to 90 is tough anyway. Many bikes of the era clearly outperforemd others in given years. The reality would be all on 89 model bikes( by 89 most has USD forks-so just hide the 2008 forks to look like 89 USD forks) the rear suspension was close( a shock rebuild away from modern), the ignition, powervalve etc was there. Hell, I could take an 89CR250 and have it look very stock -or"era" and have a bike performing like the last two stroke 250s, why because it wouldnt take much.
Then we have the motive, for many it may be what is cheap( which is important)-but the reality is it is driven by suppliers who can maybe make a few bucks with reasonalble accessories-or at least not lose their ass. How bout the historical signifigance of this era? Well, I am 40 in July and frankly, rode these bikes-but can spaek little of their historical signifigance( with a few exceptions-like 85CR500, 86KX500, 87Cr250-but that's about it). We still have many pre 85 bikes to get going(though here in US we need to allow a retrofit of drum to original disc brake bikes of pre85)-and support the classes we have.
It is not yet time to have these bikes in vintage racing-they will obsolete the others, due to thier performance, and the ease of parts, and cost in many cases.
There is a market for an old farts class of mdern bikes on smoother tracks or in a club, but that , is not vintage racing. Just the opinion of one dissenting American(Yank?), that an $3 will get cup of java