In my first outing with my MC28, it felt like mine was running out of steam around 10,000. Upon running the rpm's up a couple of times in the pits, noticed it wouldn't rev past 10,000.
My RC Valve servo may have been on it's way out or the cables too stretched, but it turns out the RC valves were way out of adjustment. (I had a spare servo and cables assembly I picked up from auction the week before for loose change and dropped it in...).
That might be the cheapest fix if it is actually out of adjustment. You should see on the tuning page how to adjust the RC valves in you're not familiar.
Dana
*edit* I'm just getting my feet wet with NSR's so maybe somebody has more experience...although us MC28 owners must be the red-headed step children around here.
