You will know if the bearings are bad, your engine will not hold a consistant tune or idle poorly. Read over the stickies on engine tuning ( not saying your new to tuning ) but it helps. I like to tune just as Ron Paris described. I tune the bottom first then the top, they come together in the end. You over clutch a S7 tho I did in the past with a Fioroni sliding clutch with teflon shoes, my engine ran like crap until I switched it out for Kyosho shoes and 1.1 springs.

I find the low-end lean when it "pings" like a 250 dirtbike after you come off a full throttle pass and come back to idle.