Grenading Stators

4 replies to this topic
  • 2grimjim

Posted October 13, 2004 - 07:22 PM


Has any one with a wr450 experienced a catastrophic stator/flywheel failure? I have recently worked on two wr450's (different owners) that have had the same problem. In both cases it appeared that the two 4mm stator screws backed out and allowed the stator to tangle with the flywheel. In both cases the stator and flywheel were destroyed. What's puzzling is how in both cases it also managed to sheer off all six of the bolts that hold the starter sprag to the flywheel. These bolts are recessed into the flywheel and none of them showed any signs of backing out or being loose prior to the carnage. I have inspected two other '03 wr450 (mine included) and haven't found anything to to be out of order, so I reassembled with plenty of loctite.

  • Indy_WR450

Posted October 14, 2004 - 05:12 AM


Not an issue with the majority here on TT. We are a tight knit group and share all our experiences. Search for posts if you think there is an issue. Your WR450's that are being raced may be used heavier then most members on this forum. :cry:

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  • ddialogue

Posted October 14, 2004 - 05:12 AM


There was a thread a couple of weeks ago on this very subject. Sorry, I'm too lazy at the moment to search for it. :cry: However, it was mentioned that Yamaha has an updated bolt part number for the six bolts that are shearing off. If I recall, the newer bolts are longer than the older ones.


Posted October 14, 2004 - 06:25 AM


This is another symptom of the '03 starter design issue, particularly if you have had the loctite tsb done. Once you loctite the flywheel something else has to give when the engine kicks back - in this case the one-way clutch bolts. Most likely the one-way bolts sheared and took out the stator. The cure is to upgrade to '04 starter parts.

'04 Starter Upgrade

  • 2grimjim

Posted October 14, 2004 - 12:09 PM


The kickback problem sounds reasonable but on both of these bikes the stator bolts had backed completely and were perfectly intact!


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