840 vs 975.

Well I’m pretty sure I destroyed some stuff on the renegade.
If I stick with an 840 ( I’m about 165 in full gear ) I can race some gncc events. Maybe 1-2 a year. Mostly do fast trail riding.

I have built heads / cams/ bored TB / exahust , ect ,ect.

Is the 975 going to reliable ? I can enter a few local run whatever hare scrambles locally to satisfy my needs. Can the 975 take 2 hours of abuse ?