When I bought my 05 WR the PO told me he had replaced the piston and barrel due damage that occured due to "it running lean when it ran-out of fuel at high speed" (he had been using it on the road). Soon after buying it I blew the head gasket when at full noise going up a long steep hill. I pulled it apart inspected everything (all OK) and put it back together with new gaskets carefully following the torquing procedure in the manual.. One thing I noticed when I pulled it apart was the front right head stud was barely finger tight - so I suspected the PO hadn't torqued the head properly. After another about 20 hours the head gasket blew again. This time a put a spanner on right front bolt and was amazed to get about 1/2 turn on it. That seemed to seal it up - but after 20 minutes it blew again - and yep, I got another 1/2 turn on the front right stud. I did this a total of 4 times - thats around 2 turns! On pulling it down it is clear that stud has stretched.
The studs are shaped/wasted, which leads me to suspect they are designed to yield on tightening. If so, it means they are designed as a one-time use.
The interesting thing is that the manual does not advise using new head bolts - unilke a lot of other things which it clearly points out should be replaced, and I (and the mechanics at local Yamaha
shops I have talked to) have never heard of this happening before.
Edited by dogerxf, February 04, 2012 - 12:12 PM.