sand inside the crankcase

[3wheelerlouie]

i found some sand inside the crankcase of my spare air cooled ATC 250R engine, will it hurt it if i just turn it upside down (top-end removed) and "flush it?? or should i take it completely apart ??? the crank spins freely and there is no "grinding" noise, its just at the verry bottom , also some was on the outside of the engine.. i am kinda wondering how it got there .......
any suggestions???

thank you ..
A.

[braunz200x]

sure if you wanted you could mix up some oil and a little bit of gas and give it a good rinse