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Port Map for the YZ250 2003+ cylinders

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I took some measurements from a stock 2003 YZ250 cylinder. Next I created a CAD drawing and exported to PDF. It prints out and matches up pretty well with all the ports.

Print at 100% size (no scaling, don't use "fit to paper"). It will fit on A size or Letter size (8.5"x11") paper.

http://freepdfhosting.com/ee4cd3edf0.pdf

[DISCLAIMER]

I ignored the chamfers on the port edges. So if you roll this into the cylinder and shine in a flashlight, the ports will show up larger than the printed lines. Also there are differences between all production parts and even from one side of my own cylinder to the other. They are castings after all and they have flaws.

This is a DRAFT VERSION, it is not perfect. I'm working on refining some of the edges, I'll add dimensions, etc and I'll update the file and thread when I'm done.

If you use this for anything, don't blame me if it causes problems.

[/DISCLAIMER]

I also have created some drawings of all the gasket surfaces, but I need to make some corrections and adjustments before I plan on sharing them.

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Very cool, thank you for sharing. Now I really wish I would have done this on my last rebuild so I could compare stock vs my bike and see what they did

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There's always next time...

It would be really interesting to see the difference in such a unique setup like your long-rod engine.

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It's interesting that the port layout is very similar to the '00-'01 CR250s. Do you have any measurements (timings or distances) on that cylinder?

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Those mechanical PV CR's had good engines.

I have all the dimensions, I will add them into the drawing when I finish it up.

Keep in mind that you have to measure how far the piston is below deck on each assembled engine to get an accurate measure of the port timing. I think the YZ piston is around .010" below the deck surface on a stock engine.

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