You pull the main valve cover off to get to them, not that hard. Use a good heavy bearing grease to hold the needle bearings in place when you drive the new 'axles' in...can't think of what to call them, axles... that'll work. Second time I did them I took the time to grind down the old axle to go in by hand, then used the new axle to take it's place which helped hold the needle bearings in place. You'll know what I mean when you see them. I started chasing widening valve clearances right about 3,000 miles on my 610, baffled me until I took apart the top end to see what was really going on.