How-To: Torque Head Bolts on a Harley Evo Big Twin


Each of the four head bolts on both cylinders of the Harley Evo Big Twin need to be tightened progressively, in four stages, to a final torque level of 42 foot-pounds. You use torque wrenches to ensure that important bolts receive the correct level of tension. Bolts hold important sections of a bike in place, such as the wheel hubs, motor mounts or heads, and they need to withstand heat, vibration and pressure. To ensure these bolts do not back out under these forces, manufacturers recommend specific torque levels, such as these for the head bolts.

  • Unlock the torque wrench at its base, spin the handle until the torque wrench reads 9 foot-pounds and lock the wrench. Tighten the head bolt numbered "1" on the forward cylinder to 9 foot-pounds. Continue with the 2,3 and 4 bolts, tightening them to 9 foot-pounds as well.

  • Return to the number one bolt, with the torque wrench set at 15 foot-pounds and progressively tighten bolts 1 through 4. Set the wrench to 25 foot-pounds and tighten all four head bolts. Finish the torque process with the wrench set at 42 foot-pounds.

  • Move to the rear cylinder, reset the torque wrench to 9 foot-pounds and progressively tighten bolts 1 through 4. Increase the torque on the wrench from 9 foot-pounds to 15 foot-pounds and tighten each of the four bolts until the wrench clicks on each bolt. Increase the torque wrench to 25 foot-pounds and tighten each of the four head bolts until the click is heard once again. Finally, increase the wrench to 42 foot-pounds and complete the last cycle of tightening, listening for the click to ensure each bolt is tightened to exactly 42 foot-pounds.

Tips & Warnings

  • When resetting the torque wrench from 42 foot-pounds down to 9 foot-pounds, first turn the wrench until it reads 0 foot-pounds and then increase the torque again until you reach 9. This ensures the torque wrench is properly calibrated.

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