Long time reader, first time post.
Timing chain tensioner.
My 06 Rage with 4500 miles on it did the same thing. Sled was 2 months out of warranty and Yamaha covered it 100% parts and labor. Would not give me a new motor but replaced crank, all timing components, All exhaust valves,pistons,rods,rings,oil pump. While it was in the shop they gave me a deal on a 07 Rage GT that I couldn't pass up. Have 5600 miles on it now and I just checked the chain and gears and everything looks fine. All I have to do I figure out my carb. problems and I'll be good to go.