My first contact with it was with a couple of old blokes with a JAP 4B, and a young bloke riding it in the 70s on regional Qld tracks, the blokes who blew some chalk dust into the carb throat after fitting new rings during a meeting, after the rider found another 500 rpm down the back straight on a longer showground track. That young bloke could sure pull on the throttle cable. A JAP 4B will run well at 7500, but at 8000 the 99mm stroke gives a sky high piston speed for the 60s tech rings to cope with. They weren't winning many races with the obsolete motor, but were having a lot of fun. Old buggas go racing with an old bike.  Almost 50 years later it starting to sound good to me.