what causes the engine to "groan" while sand riding?

[jaguar]

Could it be clutch slippage? I have new plates and springs but I use 15/50 gear oil.
It only happened when starting off in deep sand (lots of wheel spin and almost going nowhere)
thanks

 

[Sage]

Clutch chatter?

 

[GRNMCHN]

If you are running a paddle tire, then that is probably what you are hearing as it digs into the sand, and the vibrations reverb through the frame of the bike, you can probably feel it too. Paddle tire or not you are putting a big load on the engine running in the sand so it could very well be the clutch. If you are not running a paddle, get one it is soooo much easier.:D