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Yamaha WR250f 2002 cylinder head question.

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HI!

 

I have a question, if 2005 WR250f Cylinder head 5XC... will pass into 2002 engine (Cylinder head 5NL...)? If not what is the difference between this two models?

 

Thanks!

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Take this worth a grain of salt, but I believe you can do it but you also need to replace the piston.  The newer head has different valve angles.

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, but I believe you can do it but you also need to replace the piston.  The newer head has different valve angles.

 

this is mostly correct.  no other info needed.  

 

and found in the forum faq btw

 

match the piston year to the head year.

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Here is the scoop....

01 to 04 has the lower volume head. The stock piston was actually concave (dished out).

05 to 11(?) has higher volume in the head. 06-07 stock piston is a flat top.

08 to 11(?) stock piston is slightly domed for higher compression.

Not sure what is in a 12-13, 14 is obviously incompatible as it a 4 valve.

Bottom line = 05 to 09 head works on the older bikes, but be sure to use a piston from 2005 or newer. 2008 piston works good and boosts compression just that right amount.

Edited by BazookaJoe

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Here is the scoop....01 to 04 has the lower volume head. The stock piston was actually concave (dished out).05 to 11(?) has higher volume in the head. 06-07 stock piston is a flat top.08 to 11(?) stock piston is slightly domed for higher compression.Not sure what is in a 12-13, 14 is obviously incompatible as it a 4 valve.Bottom line = 05 to 09 head works on the older bikes, but be sure to use a piston from 2005 or newer. 2008 piston works good and boosts compression just that right amount.

Hi there, seems like the topic of newer cylinders on older bikes is a topic that was covered but it is the first time I hear about it. I will have to replace the cylinder on my 06 wr250 and I am wondering if an 08 is just a direct replacement. I have a wr not yz. Thx

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The cylinders will interchange just fine.

Little trivia... The earlier models (01-02) had a full skirt (the part of the cylinder below the base gasket surface), but over the years, Yam added little cut outs on the sides of the cylinder. The full skirts can be a bugger to install the piston, especially Wiseco pistons with their skimpy oil rings. But the 03 and newer cylinders, with the side cut outs are a world easier.

Helpful tip- assemble the piston into the cylinder on the workbench and then install the cylinder + piston onto the connecting rod. Saves $$ into the swear jar.

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