2006 yz450f piston markings


12 replies to this topic
  • 88motohead88

Posted October 16, 2014 - 01:05 PM

#1

This is a new piston with maybe 3 hours riding time. Any ideas what causes this?

Attached Thumbnails

  • 1413493522315.jpg


  • grayracer513

Posted October 16, 2014 - 02:28 PM

#2

The piston is hitting the head is what's happening.  As it's only hitting on the exhaust side, it could be too much rock/tilt at TDC due to excessive piston clearance, or a lot of carbon on the head on that side.  Otherwise, it would be due to inadequate deck clearance (the distance between the top of the piston and the top of the cylinder at TDC).



  • 88motohead88

Posted October 16, 2014 - 03:19 PM

#3

It's a brand new piston and cylinder so how does the rock/tilt work? So I got a bad cylinder and piston? Can I still use it?

  • 88motohead88

Posted October 16, 2014 - 03:22 PM

#4

Sorry what I'm trying to say is the piston clearance you mentioned shouldn't be excessive because it's a brand new cylinder and piston right?

  • stevethe

Posted October 16, 2014 - 03:35 PM

#5

Sorry what I'm trying to say is the piston clearance you mentioned shouldn't be excessive because it's a brand new cylinder and piston right?


You may have some mismatched parts there. You should contact the manufacturer with pictures.

  • BMcEL

Posted October 16, 2014 - 03:39 PM

#6

Where did you get the 'new' cylinder from?  Or was it a remanufactured cylinder?  If it's a reman, I wouldn't be surprised if they decked the cylinder and/or the head and took too much off.  Regardless, you should start by measuring the deck clearance.



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  • 88motohead88

Posted October 16, 2014 - 03:49 PM

#7

It was from cylinder works. Brand new. So if I run this like this now that the piston and head is "shaved itself " basically by am I gonna blow it up? It ran great but the rod broke, I've got a new used bottom end.

  • 88motohead88

Posted October 16, 2014 - 03:50 PM

#8

The head and piston show the signs of contact, I'm wondering if the damage has been done won't it be ok now?

  • stevethe

Posted October 16, 2014 - 04:08 PM

#9

The head and piston show the signs of contact, I'm wondering if the damage has been done won't it be ok now?


Definitely not. You do not have enough clearance and I would not trust the beating the piston took as it being clearanced now.

  • 88motohead88

Posted October 16, 2014 - 04:09 PM

#10

Ok any suggestions?

  • stevethe

Posted October 16, 2014 - 04:18 PM

#11

Ok any suggestions?


If everything else is okay you could have the piston shaved down to make the proper clearence.
You should however find out why it hit. Was the head decked or material taken off from it.

  • mx369

Posted October 16, 2014 - 07:22 PM

#12

What gaskets are you using? Check thickness of old and new.



  • grayracer513

Posted October 17, 2014 - 06:21 AM

#13

Start with the piston. measure from the pin bore to the top of the crown and compare to the original.







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