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Author Topic: Yz490 piston  (Read 1868 times)

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Offline POM

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Yz490 piston
« on: November 21, 2015, 10:39:59 am »
Does anybody know the difference between the 82/83 piston and 84 onwards?.......part listings on eBay seem to suggest their different.......
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Offline tony27

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Re: Yz490 piston
« Reply #1 on: November 21, 2015, 12:23:09 pm »
Likely to ring pin location, earlier motors are sideport like the 465s then then they changed to central exhaust port. Reed valve shape changed as well
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Offline Rupert Prior

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Re: Yz490 piston
« Reply #2 on: December 28, 2015, 02:45:39 pm »
there is a difference in the compression heights (pin to crown height). early is 40mm and late is 39mm, I don't know the point they changed and I have only seen it in after market pistons. it causes problems with the squish clearance, so the barrel has to be shimmed to match.
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