If you drive your KB in loose impediments aka loose soil, loose sand (bad idea), loose gravel it is a good idea to remove the tunnel protecting your Main Drive shaft for a cleaning. Once clean re-assemble protection! I had the unfortunate experience of getting a smell pebble down there and every time throttle was given the shaft spun and either scraps, picks up or can even wedge its self so that damage is great. Removal is simple, WD-40 the shaft so that theres some slippery protection and you will be good to go hope this helps ppl.
IMo sand = sand paper to plastic parts !