The 'Definitive Guide to Rollerisation'   This is something I've been meaning to do for a while as, despite the very youngest flat tappet bikes being nine years old now there are still a large number of them out there and in this post I'll try and cover both the procedure and pitfalls liable to be met during the rollerising process.   Firstly let's cover which bikes need rollerising.   Most importantly it is ONLY the four valve per cylinder, (8 valves all told so I'll refer