I don't know Dan,
I use a power washer sometimes on my 4x4 trucks, but not sure it would be a good idea for my scoot. Before you power wash you had better do some bagging and tapeing where you don't want unwanted water to go. This would be time consuming and therefore not worth the effort IMHO.
I suppose it would be ok to use it on the tires and rims, but I just use a brush and soapy water and that works just fine for me.
I would think that you could also push in the sand etc. with the pressure also these clean by using the water and soap for abrasion . I would just use a hose with lots of volume and low pressure. I think you would be asking for trouble.