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Runafter

2007 YZ450 Head Torque

4 posts in this topic

I have found some torque specs in the owners manuel to be incorrect. On a previous top end rebuild bike was burning oil. Rings and bore were completely gone about 25 hours. Could this be from over Torqeing the head? I went by the manuel 22 ftLBS. to set gasket, Loosen 14 ftlbs and 180 degrees.

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http://www.thumpertalk.com/topic/873863-cylinder-head-tightening/

Here is thread from the "common mods and issues" sticky at the top of the yz450 etc. forum. GrayRacer chimed in and explained the torque sequence (the same one you have described.... as well as the manual). I have followed this sequence several times now, with piston replacement, without, head gasket change, valve work.... etc... and have had no failures that you have mentioned. The only other thing I can theorize as a possible issue, is if you did any piston work with slight improper maintenance. No discredit to you of course. I just cant imagine there being much of anything cylinder head torque can do to the bore if done properly, in steps, according to the manual.

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The process described in the manual ends up generating about 50 ft/lb of torque. That can vary some because using torque at the bolt head on a bolt that long produces inconsistent true clamping force over the bolt set, whereas the idea of angle torquing in the first place is to have consistent clamping force regardless of torque, thread friction, bolt twist, etc. If it's done right, it will not distort the bore or cause any problems.

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Thanks for the info guys. you also answered my second question about lube for the treads.

Runafter

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