Well what really helps is if you hear like a scraping nose in the bearings then thats most likely sand so then use brake clean and spray the bearings and let it sit for a few seconds and then blow them out with compressed air and then oil them with WD-40. This works very well on my rc. I also professionally race Go Karts and I use this technique a lot for cleaning the bearings. Hears a picture of the kart I race. [img][/img]
Thanks