Head Gasket Re-useable? - Yamaha YFZ450 Forum : YFZ450, YFZ450R, YFZ450X Forums
 
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post #1 of 8 (permalink) Old 06-17-2007, 09:34 PM Thread Starter
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I've got the top end out of my 07, maybe has 3 hours on it... I'm going back with a hi-comp piston, but someone told me I should replace the head gasket... The other two I've done I did not replace it but experienced no problems. What do you think?
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post #2 of 8 (permalink) Old 06-17-2007, 09:47 PM
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You got lucky the first couple times. Replace it, and clean the mating surfaces.

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post #3 of 8 (permalink) Old 06-17-2007, 09:49 PM
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Agreed ^^^

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post #4 of 8 (permalink) Old 06-18-2007, 01:16 AM
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The head gasket is MLS I believe, which crushes when you tighten down the head bolts and conforms to any unevenness in the cylinder or head surfaces. If you reuse the gasket, you don't get the crushing effect since it can only happen once. So unless you get the gasket on EXACTLY the same way it came off, it won't seal right and it will leak. It's not worth the risk IMO.

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post #5 of 8 (permalink) Old 06-18-2007, 07:23 PM
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and replace the head bolts toooo
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post #6 of 8 (permalink) Old 06-18-2007, 08:25 PM
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Quote:
and replace the head bolts toooo[/b]

Is that really necessary? I guess if going with a new cylinder and all it makes sense. The bolts stretch a little, I guess.

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post #7 of 8 (permalink) Old 06-18-2007, 08:55 PM
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Its not always needed. If you are going with a high compression motor or a larger cylinder, its wise to do. Some have gotten by with reusing original head bolts. It can get expensive to replace the head gasket and bolts if you need to tear into the motor often.

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post #8 of 8 (permalink) Old 06-18-2007, 09:11 PM
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The head bolts are torque to yield bolts, meaning that they are stretched to near the point of breaking. This is done when putting the additional angle on the bolts. However, on my build, with a 14:1 piston, I reused the stock bolts because I was short on time and the local dealer didn't have any in stock. They may be good for one or two rebuilds, but it's always a good idea to replace them just in case.

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