I'm fresh out of a week recurrent training from an overhaul shop, the rr 300 is the old technology back end with a centrifugal compressor up front.the reason for the cool down is to get the core below 450 degrees which is where carbon forms. I like 3 minutes on our R2 as we had lock up at times with 2 minutes cooldowns, and none on the 3. making sure the 6&7 struts upper and lower are cleaned well on the inside helps also , also the oil tube with the stem out the top is the new style and thus the 200 cc oil flows we see..