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which piston?

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hi, I will be doing the top end on my 2009 yz250 just wondering which piston is best, I can't see any letter on my cylinder so I was going to go wiseco.

Do you have any preferances. Also should I go with Yamaha gasket or after market. On my yz125 I found yamaha base gaskets thicker and it ran better on these.

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The general consensus is that both cast pistons and forged pistons have their ups and downs. Cast pistons can crack or shatter while forged pistons are more likely to cold seize. I opt to go with Wiseco myself, with Cometic gaskets. If you choose to go with an OE piston make sure you price out Pro-x, since they should be cheaper, and are made by the same manufacturer. You shouldn't need to know your piston size, as D size piston is recommended on a used cylinder.

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D size is recommended with a used cylinder as said above, I've run oem and Wossner pistons in mine with great results in the past however i have just purchased a Wiseco to see what all the hype is about. It's easier to buy aftermarket out here also. The Wossner does come in different sizes also and would recommend it to anybody, however i try to use oem gaskets wherever possible.

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Go the wiseco. They are a top unit and give you the added peace of mind that they're not going to grenade as easily if left in service for too long.

Just be careful that you warm your bike up properly before riding when running a wiseco - they are more prome to cold seizure than the OEM cast unit.

With the wiseco, its a 'one size fits all' affair. You don't buy an a, b, c or d spec piston.

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Depending on the cylinders size, if you have an A cylinder or a B get wiseceo, if yiu have a C or a D I would look for someone's product which comes in 4 sizes, A, B, C and D.

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