Back then I just thought it was some type of machining debris from manufacturing. Replaced boss, pressure plate, and fiber plates. 6 months later it has happened again. What's causing this? Anyone fixed this problem? By going to one of the aftermarket clutches?
Also, in less than 18 months riding about once a month,
-my cam chain has stretched so bad it jumped time,
-there's so much clutch material in the oil (changed every 2 to 3 days riding) that I think the system is starved for oil from stopping up the oil inlet screen,
-the bushing surfaces on the cams are scored,
-the top end ring gap at the max on the top ring and double the max gap on the 2nd ring,
-The valves don't seal perfectly (tested by brake cleaner leaking through)
In the last 10 years, having owned a 99 YZ400, which I rode twice as hard and put 10 times the usage, a 02 YZ426, and now an 09 YZ450, given the reliability of the new 450 compared to older motor design, I have come to the conclusion that the new motors are junk. Sad day for me but in my mind, the Yamaha 4 strokes are not what they use to be.
Edited by Phil_S, June 23, 2011 - 03:54 AM.