The 1985 AMA 500cc National Championship would be the sixth and final championship for Broc Glover who’s career included 50 National wins, a number that was only recently topped by Jeremy McGrath and Ricky Carmichael. It would prove to be one of the most difficult championships as Glover was hampered by a nagging wrist injury and a less that competitive motorcycle. The AMA instituted the production rule at the beginning of ’85 which meant Broc would compete for his third 500cc National Championship on what many considered one of the worst motocross machines ever built.
The YZ490 was introduced in 1982 after a solid run for the YZ465. Sadly, the 490 was heavier than the 465, nowhere near as reliable, difficult to start, had grim suspension, vibrated, and was impossible to jet. This coincided with the popularity of 500 class machines waning, so Yamaha stuck with this poor design up until 1991.
If you jetted it rich enough to keep from seizing, it would blubber, foul plugs, and produce little power. If you jetted it to run strong, it would detonate and eventually seize. It came with air leaks, wandering ignition, gimpy motor mounts, and a bad case of Yama Swap! Yamaha issued a mountain of service bulletins to try and fix the problems. None of them worked!
One of the features that was unique on the 1985 model was the BASS system or Brake Actuated Suspension System. The idea was to decrease compression damping when the rear brake was applied. Most riders found the system didn’t work and in 1986 the Bass was removed.
The pictured example didn’t have any of these problems! Why, the bike was a present from Yamaha to Broc Glover and he has never started or ridden the bike. The bike is on loan to the Early Years of Motocross Museum.