That year YZ490 was the first Open Class 2 stroke I ever rode, it had the proper head mods and porting to get rid of the detonation and blubbering. I was racing a YZ125 and a Maico 250 that year and got to ride the bike at my practice track. I remember twisting the throttle WFO and thinking I wasn't going very fast because it wasn't screaming at 10,000 RPM, until I hit the first corner going about 20 mph faster than I expected and blew right through!!! Even though I am faster around a track on a 125, I still love Open Class 2 strokes!!!! Your bike looks great!