If you dump on a lid, you will run rich by a jet or two.
Sand is going to make it work harder and it will tend to run hotter.
One way to lean it out is to jet back.
The other way is to change your oil/fuel ratio to 25:1, this will lean out the fuel/air mix, but give extra lubrication which should help with the added heat.
My lad and I ride very hard in extremely hot situations, over 100 degs at times.
The 25:1 mix not only gives peace of mind, that there is adequate oil, but adds a little more compression.
Im not saying that this is what you should do, but it is an option, I know it works well for me.