How to remove the head??


8 replies to this topic
  • Boltos

Posted January 08, 2009 - 07:01 AM

#1

I have not been into to this bike to this level. Do I need to remove the engine from the frame to get the head off? Can it be done in the frame?

2007 YZ450f
Thanks

  • Wiz636

Posted January 08, 2009 - 07:06 AM

#2

Yes, it can be done without removing the motor.

  • William1

Posted January 08, 2009 - 07:07 AM

#3

First, you need to sit down with a snifter of Cognac and read the shop manual.
http://www.yamaha-mo...ice/manuals.jsp

It is a fairly easy job.

  • grayracer513

Posted January 08, 2009 - 07:18 AM

#4

On my '06 that I put rings in, I found there were two head bolts that could not be removed with the head sitting in position. IIRC, it was the left front and right rear. In one case, I could tip the head and remove the bolt, in the other, I had to rotate the head out of place to do it. Going back together, I put these two bolts into the head and threw a rubber band over them to hold them up high enough that the anti-seize lube on the threads wouldn't get onto the head gasket. The only other thing is that you're sort of forced to skip re-lubing the threads between the initial and final torque down. It's a little annoying, but not bad.

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  • Boltos

Posted January 09, 2009 - 03:45 AM

#5

...to hold them up high enough that the anti-seize lube on the threads wouldn't get onto the head gasket. The only other thing is that you're sort of forced to skip re-lubing the threads between the initial and final torque down. It's a little annoying, but not bad.


Ok, I got the cams, head, and cylinder off last night OK. But your statement above throws me. I'm thinking locktite on the head bolts during reassembling and you mention anti-seize. Please elaborate.

Also, I am not familiar at all with your mention of re-lubing threads between initial and final torquing of the head bolts.

I should volunteer that most of my wrenching has been vintage BMWs in the last couple of years, and I must be unfamiliar with modern requirements.

  • grayracer513

Posted January 09, 2009 - 06:52 AM

#6

I'm thinking locktite on the head bolts during reassembling and you mention anti-seize. Please elaborate.

Also, I am not familiar at all with your mention of re-lubing threads between initial and final torquing of the head bolts.

Please don't tell me you are working on this bike without a manual.

The Head bolt torque procedure is called angle torquing:
  • Apply Moly Disulfide grease to the threads and contact surfaces of the head bolts.
  • Torque to 22 ft/lb (30 Nm) in the prescribed pattern.
  • Loosen the bolts completely, reapply MoS₂ grease, and re-torque to 14 ft/lb (20 Nm)
  • Mark each head bolt and turn each one 90 degrees tighter, then another 90 degrees tighter for a total of 180 degrees

Here's a link to the manual:
http://www.yamaha-mo...ice/manuals.jsp

In nearly 40 years as a professional technician, I have never once even considered using Loc-Tite on a head bolt on any engine, nor seen it recommended by any manufacturer or individual engine builder. It's a bad idea.

  • Boltos

Posted January 09, 2009 - 09:57 AM

#7

Please don't tell me you are working on this bike without a manual.

In nearly 40 years as a professional technician, I have never once even considered using Loc-Tite on a head bolt on any engine, nor seen it recommended by any manufacturer or individual engine builder. It's a bad idea.


I do have the manual, but since my task was disassembly, I have not read the section on assembly yet. It will be several weeks before it is ready for reassembly, but thanks for the tip.

I actually have never used Loctite on the head assembly, but on just about every other bolt, except exhaust. On BMW race bikes, it had better be safety wired, or locktite and RTV or it's gone. I'll try and be more precise in my comments.:thinking:

  • PAdaytonaman

Posted January 09, 2009 - 07:05 PM

#8

Have you ever seen torque values decrease as the aluminum parts have been tightened a few times. In other words, if the recommended torque is x, i have noticed that in aluminum parts, its sometimes a dangerous practice to try to retorque to the same spec. Stripped bolts, etc, have you ever seen this, and what do you do?

Please don't tell me you are working on this bike without a manual.

The Head bolt torque procedure is called angle torquing:

  • Apply Moly Disulfide grease to the threads and contact surfaces of the head bolts.
  • Torque to 22 ft/lb (30 Nm) in the prescribed pattern.
  • Loosen the bolts completely, reapply MoS₂ grease, and re-torque to 14 ft/lb (20 Nm)
  • Mark each head bolt and turn each one 90 degrees tighter, then another 90 degrees tighter for a total of 180 degrees

Here's a link to the manual:
http://www.yamaha-mo...ice/manuals.jsp

In nearly 40 years as a professional technician, I have never once even considered using Loc-Tite on a head bolt on any engine, nor seen it recommended by any manufacturer or individual engine builder. It's a bad idea.



  • grayracer513

Posted January 09, 2009 - 08:16 PM

#9

In a well made engine assembly, you should be able to reassemble the top end several times without worrying about stuff like that, particularly if you follow all the correct procedures, such as lubing the threads when called for. The threads are definitely stressed each time the head is torqued down, and over time, they can fail if they are cut in low grade material. But to cut back on the torque is to cut back on the clamping force that provides the seal at the head gasket and anchors the top end in place while you're converting fuel into 50 horsepower. If you think the threads are weak, or will be a problem, have a machine shop install steel thread inserts, or replace the bolts with studs.





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