I’ll say this . The Desert X uses the 959 engine which is a derivative of the 821 .
We’ve had two Monsters in with that engine that were very noisy.
When we took them apart they both had massive play on the crank, we discovered that the crank doesn’t have a main bearing just a big bush.
This smacks of cost cutting by Audi since they took control.
My boss said if he had one he would junk the engine and fit an air cooled 803 engine from a Scrambler.