WR450 Cylinder Head Torque instructions
Posted June 25, 2009 - 05:27 AM
The Yamaha service manual says to torque the cylinder head bolts to 20 ft lbs, the losen and re-lube the bolt threads, then torque to 14 ft lbs, then turn each bolt 90 degrees, then another 90 degrees for a total of 180 degrees (one half turn)...
THIS SEEMS WAY THE F**K TOO TIGHT TO ME.
I followed this procedure up to the first 90 degree turn, then stopped out of fear of stripping the bolt theads in the case or warping the head.
Anyone out there have any thoughts regarding the procedure called out in the manual???
Posted June 25, 2009 - 05:31 AM
Posted June 25, 2009 - 06:23 AM
I've done it on 3 bikes and never had any problem. It is tight but seems to work fine. Never had a head gasket fail afterwards either.
We rebuild my dads 06 and have ZERO issues...I would follow the manual:thumbsup:
Posted June 26, 2009 - 02:01 PM
Posted June 27, 2009 - 12:52 AM
That's the correct procedure. Torque, loosen, retorque to 14, the rotate 180 degrees in two steps. If you use a torque wrench as you do this, you'll see that it is not much different from the old spec of 27 ft/lb.
I would say that 180 degrees would have put me WAY over 27 ft lbs... I stopped at 90 degrees (1/4 turn) because it felt like I could go no farther without damaging something. This is the reason for my post.
Did I mention that I only removed & reinstalled the head without disturbing the cylinder base gasket... Perhaps this is the reason?
Posted June 27, 2009 - 10:34 AM
If you do not turn the bolts the full 180, you will be under torqued.
Posted June 27, 2009 - 12:29 PM