Anouther Bog problem for you lot!

Perhaps your problem is fuel flow to the carb. If you have an in line fuel filter remove it for testing. While you have it out or just have the fuel line disconnected drain fuel into your gas can from the gas tank and see if the flow is good for a few minutes straight--to be sure the filter in the tank is not a problem and to be sure the tank is properly vented. Your engine may be starving rather than bogging.

If you have been working on your bike--there is a good chance that the gas is old drain it all out--burn it in somebody's car and start fresh on your premix. Also since your found dirt in your carb--find out where it came from and be sure it does not happen again. Take the plug about 15mm out of the bottom of the carb bowl and clean it before replacing. It never hurts to drain a little fuel through the carb to wash things out while you have the drain plug out.

Let us know how you get along. Cheers John

Be sure to look closely at the float needle tip and seat. I fould some small bits of gasket (off gas cap) lodged above the seat that would trap the needle it off the seat in the used KDX I just purchased. Could not figure out why after adjusting the floats it was still pissing gas. Found this by spraying carb cleaner into the fuel inlet and then looking closely at the seat area. Good luck!