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YZ450 New piston install on bike?

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Yes you can, it is very easy. The most difficult part is getting the valve cover back on, but once you figure out a technique it's not so bad.

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Yes, I always do it in the frame. With the 06 it is tricky to get one of the head bolts out because it hits the frame rail before the bottom of the bolt it out of the head, you need to remove the others and loosen this one all the way, then lift the head up and tilt it forward to get this bolt out. Other than that it isn't too bad.

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if i recall, the one time i did pull the head off and cylinder off my 06, that yeah there was 1 or 2 bolts that were a bit hard because of the frame, and also getting the head i think off is a bit of a hard one, other 2x ive had the whole engine out,

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Got the cylinder off (was pretty easy) and it is scored pretty good so the next question is do I try and salvage or replace? I am not sure if this is something that will need to be re-plated or can just be bored out. A new OEM cylinder, piston, etc. is about $450.....

th_YZRebuild008.jpg

th_YZRebuild007.jpg

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Your cylinder is not borable. Replate or replace. I found a new OEM cylinder & piston & rings on ebay for $400 for my 08

The stock cylinder head is not borable to ANY degree? Not even because of MILD scoring?

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The cylinder HEAD is never boreable.

The CYLINDER on YZF's, as with most modern high performance motorcycle engines, is plated with Nikasil, an extremely hard nickel/silicon/chrome alloy. When the plating wears beyond tolerance (or all the way through as the gray area at the top of yours shows), it has to be re-plated and diamond honed back to it's proper size.

The practice of boring for wear is not possible, and no oversized pistons are made for the purpose, only grossly oversized ones for big bore kits. Really minor scratches are dealt with by deglazing with a ball/brush hone, but yours is way past that.

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The cylinder HEAD is never boreable.

The CYLINDER on YZF's, as with most modern high performance motorcycle engines, is plated with Nikasil, an extremely hard nickel/silicon/chrome alloy. When the plating wears beyond tolerance (or all the way through as the gray area at the top of yours shows), it has to be re-plated and diamond honed back to it's proper size.

The practice of boring for wear is not possible, and no oversized pistons are made for the purpose, only grossly oversized ones for big bore kits. Really minor scratches are dealt with by deglazing with a ball/brush hone, but yours is way past that.

Im not the OP...i was just curious. Thats what i get for being a lifelong 2 stroke rider before taking the plunge on a big 4T. (never going back by the way)

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Okay, new question. I have been reading the manual and if I understand it correctly the head bolts need to be torqued, then pulled out, re-torqued and then tightened a 1/2 turn past the torque setting...I am understanding that correctly or am I misunderstanding...?

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the head torques is very confusing and that sounds about right......but I do not remember off the top of my head if it was 1/2 or not.

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Okay, new question. I have been reading the manual and if I understand it correctly the head bolts need to be torqued, then pulled out, re-torqued and then tightened a 1/2 turn past the torque setting...I am understanding that correctly or am I misunderstanding...?

it's half a turn total.. 1/4 turn at a time though.

the difference in the reading from a torque wrench when you factor in how clean the threads are, oil vs a little oil vs bone dry, etc. can be huge. this "angle torque" method is supposed to help make things more equal and is pretty common on newer car engines..

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The manual says to use "molybdenum disulfide grease" on the threads, I called one of the local parts stores and they had no clue what I was talking about. Is there a name brand or some sort of trade name that I should look for? Can I substitute with something else?

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