Head torque spec or angle torque?


6 replies to this topic
  • SDBSKI

Posted June 22, 2011 - 09:01 PM

#1

I'm assembling my YZ426 and the head torque spec is 32Ft Lbs. Is it better to use the YZ450 procedure of angle torquing?

  • todds924

Posted June 22, 2011 - 09:30 PM

#2

you can use either one...but do it in stages if you just go with 32 ft lbs.

  • grayracer513

Posted June 23, 2011 - 06:39 AM

#3

Also, the manual is not real clear on one important point: The 4 main cylinder head bolts need to be lubed with assembly lube or another high pressure moly grease at the threads AND at the bolt flange where they bear on the washers. Failing to do this will result in inadequate and/or uneven clamping force applied to the head.

Angle torquing is definitely a more accurate method, but until I was able to determine how much torque is produced by turning 180 degrees past 14 ft/lb, I think I would stay with the specified 32 ft/lb for the 426. As Todd says, run them up in at least 3 progressive steps using the pattern in the manual.

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  • SDBSKI

Posted June 23, 2011 - 05:14 PM

#4

Thanks. The Yamaha head bolt threads did have moly grease on them when I disassembled it. Angle torquing worked great on my VW diesel with stretch bolts.

  • SDBSKI

Posted June 23, 2011 - 05:22 PM

#5

My yz400 manual says 29 ft lbs. The yz426 manual says 32. Looks like Yami changed the procedure for the redesigned YZ450 engine to the angle torque method.

  • todds924

Posted June 23, 2011 - 10:43 PM

#6

My yz400 manual says 29 ft lbs. The yz426 manual says 32. Looks like Yami changed the procedure for the redesigned YZ450 engine to the angle torque method.

Yeah but I've put big bore kits in new 450's and Athena specifies 32 Ft lbs.

  • Schpenxel

Posted June 24, 2011 - 05:09 AM

#7

Also, the manual is not real clear on one important point: The 4 main cylinder head bolts need to be lubed with assembly lube or another high pressure moly grease at the threads AND at the bolt flange where they bear on the washers. Failing to do this will result in inadequate and/or uneven clamping force applied to the head.


Wish I had known that before I put mine back together lol.

Oh well, if the head gasket blows again I'll know next time.





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